RESEARCH REPORT 127. Measurement and modelling of combustion products from flueless gas appliances HSE

Transcription

1 HSE Health & Safety Executive Measurement and modelling of combustion products from flueless gas appliances Prepared by BRE Environment for the Health and Safety Executive 2004 RESEARCH REPORT 127

2 HSE Health & Safety Executive Measurement and modelling of combustion products from flueless gas appliances Stuart Upton, Dr David Ross and Bridget Pierce BRE Environment Division Bucknalls Lane Garston Watford WD25 9XX Concentrations of combustion products emitted from a range of flueless gas appliances have been measured in a chamber capable of being ventilated in a controlled and reproducible manner, including worst case simulations that would be experienced in extremely air-tight rooms. This enabled subsequent prediction of the likely concentration of combustion products for a range of ventilation provisions, room sizes and potential uses of the flueless gas appliances. In the absence of UK indoor air quality guidelines, the concentrations of combustion products emitted have been compared with the World Health Organisation (WHO) guidelines and HSE Occupational Exposure Standards (OES). When ventilation in the chamber was through purpose-provided openarea ventilation (as specified by the appliance manufacturer or BS : 2000), s of all combustion products were elevated, with carbon dioxide (CO 2 ) in particular reaching concentrations much higher than the HSE OES value. Even when mechanically provided with higher and more typical s of ventilation, concentrations of CO 2 in the chamber higher than the value set for the HSE Occupational Exposure Standard (OES) were measured. Modelling using the BREEZE program showed that the concentration s set for the HSE Short-Term Exposure Limits for CO 2 and carbon monoxide (CO) will rarely be exceeded within typical UK dwellings. However, those for the HSE eight-hour OES for CO 2, and the WHO guideline concentrations for CO are much more likely to be exceeded in situations where there is prolonged use of a flueless appliance. For nitrogen dioxide (NO 2 ), it is very unlikely that the HSE limits will be exceeded in dwellings, but the WHO guideline concentrations will be commonly exceeded. The current guidance given within BS 5440:2 is for the installation of purpose-provided open-area ventilation of at least 100 cm 2 in rooms where flueless heating appliances may be fitted. The build up of pollutants to concentrations in excess of the recognised HSE and WHO guidelines was not prevented by the purpose-provided ventilation currently required within BS This could be exacerbated as dwellings are made more airtight to meet the increasingly strict requirements of the Building Regulations, unless other ventilation provisions in homes (windows, fans, passive stacks etc.), as required under the Building Regulations are also used in practice. This report and the work it describes were funded by the Department of Trade and Industry (DTI) and the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect DTI or HSE policy. HSE BOOKS

3 Crown copyright 2003 First published 2003 ISBN All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) without the prior written permission of the copyright owner. Applications for reproduction should be made in writing to: Licensing Division, Her Majesty's Stationery Office, St Clements House, 2-16 Colegate, Norwich NR3 1BQ or by to hmsolicensing@cabinet-office.x.gsi.gov.uk ii

4 FOREWORD BY DTI/HSE The use of flueless gas appliances, for domestic cooking and heating purposes, has been widespread over many years, and continues to be so. Such appliances are usually covered by specific product or installation standards, and all new appliances are subject to certification by an independent Notified Body against compliance with the essential safety requirements of the Gas Appliances Directive (enacted by the Gas Appliances (Safety) Regulations 1995 (GASR)). The Certification process includes an assessment of the manufacturer s installation instructions, and the appliances are currently being installed to these instructions and British Standards installation specifications. However, questions have arisen over the possible health risks from the combustion products emitted by such appliances in normal operation. In order to start to assess any possible risks posed by flueless gas appliances, information was required on the type and concentrations of the emission products. The Department of Trade and Industry (DTI) and HSE, therefore, agreed to co-sponsor the work of BRE, reported here. It should be noted that the appliances were chosen at random as representative of their type, and the work should not be construed as a report on individual manufacturers appliances. The DTI have responsibility for ensuring only safe products may be placed on the market, in this instance under the GASR, while HSE has responsibility for appliance installation requirements under the Gas Safety (Installation and Use) Regulations Therefore, the question of the suitability of the use of flueless gas appliances is a matter of joint responsibility. To this end, DTI/HSE have also been assessing information obtained in a previous study* 1, carried out by Advantica Technologies Ltd for HSE. This and the present (BRE) work has been carried out against a background of proposed changes to HSE occupational exposure standards for certain combustion products and an increasing awareness of indoor air quality issues. Currently, there are no UK published standards for domestic indoor air quality, but guidelines are being considered by the Department of Health (DoH) and its advisory committees. In the absence of published information, advice was requested from the DoH Advisory Committee on Medical Effects of Air Pollutants (COMEAP), as to acceptable indoor air s for the pollutants emitted from the flueless gas fires examined in the previous study. The Advisory Committee have recommended comparing the of pollutants with guidelines and standards published by the World Health Organisation (WHO) *2 and the Expert Panel on Air Quality Standards (EPAQS) *3, 4. The report references the WHO guidelines *5, but comparison is also made with HSE occupational exposure standards where no WHO guideline is published. It is important to stress that, while pointing to a possible health effect, the raw comparisons provide no indication of risk or significance. It should be noted that some manufacturers dispute the validity of the previous study, pointing out that they represent a worst case scenario that would seldom, if ever, be encountered in practice. Similar arguments may be directed to parts of this study, which as the report acknowledges, includes some experiments simulating emissions from appliances into extremely airtight rooms and appliances operating in fault modes. However, the basic rationale for this approach is to provide sufficient information to subsequently enable likely concentrations of combustion products to be predicted for a iii

5 wide range of ventilation provision, room size and potential use of the gas appliances. Such predictions can only be based on work where all the parameters can be controlled, e.g. in a test chamber as used in this case. This report contains examples of predictions covering those appliances with the worst and typical emission rates for the main combustion products studied. Care should be taken in interpreting these predictions and applying them to the other appliances, as the operating period on which a particular prediction is based may not be representative of the normal period of use of those other appliances. While acknowledging the limitations of this laboratory study, DTI/HSE are publishing this report in the public interest, as a contribution to the wider discussion on product and installation standards for flueless gas appliances. As part of this debate, DTI/HSE are working closely with relevant bodies e.g. the British Standards Institution (BSI), to ensure that the implications of this work are explored in developing future standards and guidelines for flueless gas appliances. *1 Hill RW and Marks S, Flueless gas fires concentration of carbon monoxide, carbon dioxide and nitrogen dioxide, and particulate produced in use, HSE RR 23/2004. *2 World Health Organisation. Air Quality Guidelines for Europe. Second Edition. WHO Regional Publication, European Series, No 91. Copenhagen: WHO Regional Office for Europe, *3 Department of the Environment. Expert Panel on Air Quality Standards. Carbon Monoxide. London: HMSO, *4 Department of the Environment. Expert Panel on Air Quality Standards. Nitrogen Dioxide. London: HMSO, *5 World Health Organisation. (1999). Air Quality Guidelines. WHO, Geneva. From [The guideline s from this reference: CO 8-hour mean of 9 ppm and NO 2 1-hour mean of 105 ppb; are slightly different from those quoted by COMEAP from reference * 2 : CO 8-hour mean of 10 ppm and NO 2 1-hour mean of 100 ppb. The differences arise from the conversion of the guideline values, which are quoted in microgramme/m 3 to ppb at standard temperatures of either 20 o C or 25 o C.] iv

6 EXECUTIVE SUMMARY This is a report on measurements and modelling of the combustion products emitted from flueless gas appliances. Measurements were made using a range of such appliances, at varying firing rates, in a controlled chamber, including worst case simulations that would be experienced in extremely air-tight rooms. Ventilation in the chamber was either in the form of purpose-provided vents in the chamber walls, or at controlled air exchange rates via a mechanical ventilation system. This enabled subsequent prediction of the likely concentration of combustion products for a range of ventilation provisions, room sizes and potential uses of the flueless gas appliances. Concentrations of carbon dioxide (CO 2 ), carbon monoxide (CO), nitrogen dioxide (NO 2 ), nitric oxide (NO) and oxygen were monitored, together with ultrafine particles, aldehydes and fuel usage. In the absence of UK indoor air quality guidelines, the concentrations of combustion products emitted have been compared with the World Health Organisation (WHO) guidelines and HSE Occupational Exposure Standards (OES). When ventilation in the chamber was through purpose provided open-area ventilation (as specified by the appliance manufacturer or BS : 2000), s of all combustion products were elevated, with carbon dioxide (CO 2 ) in particular reaching concentrations much higher than the HSE OES value. Even when mechanically provided with higher and more typical s of ventilation, concentrations of CO 2 in the chamber higher than the value set for the HSE Occupational Exposure Standard (OES) were measured. Catalytic converters fitted within some of the appliances reduced emissions of CO, through conversion to CO 2. However, these catalysts only worked well at the higher burn rates where outlet gas stream temperatures were also high. Higher concentrations of CO than the specified HSE 8-hour OES concentration were produced from the pilot light of one of the appliances tested. This was a result of both an incorrect setting of the pilot light gas pressure (as supplied to BRE) and the poorly designed position of the pilot light relative to the decorative logs that formed part of the appliance tested. Elevated concentrations of nitrogen oxides (NO x ) were emitted into the room by these appliances, with the WHO 1-hour mean guideline concentration of 105 ppb for NO 2 being exceeded in most of the tests conducted. The WHO 30-minute guideline concentration of 100 Pg m -3 for formaldehyde was exceeded in a small number of the tests. Acetaldehyde emissions were low. The number concentration of ultrafine particles within the chamber was always raised during tests, with most tests showing a marked increase in the number of particles from background concentrations of around 10,000 particles cm -3 of air to in excess of 500,000 particles cm -3. Higher concentrations of ultrafine particles in the chamber coincided with higher burn-rate tests and tests with lower ventilation rates. Still higher rates were recorded during the burn-in tests on new appliances. There are currently no health standards in place for exposure to ultrafine particles. BREEZE modelling was conducted to predict the likely resulting concentrations of pollutants within typical UK dwellings. It showed that the HSE STEL for CO 2 and CO will rarely be exceeded. However, the HSE eight-hour OES for CO 2, and the WHO guidelines for CO are much more likely to be exceeded in situations where there is prolonged use of a flueless v

7 appliance. For NO 2, it is very unlikely that the HSE limits will be exceeded in dwellings, but the WHO guideline concentrations will be commonly exceeded. The current guidance given within BS 5440:2 is for purpose-provided open-area ventilation of at least 100 cm 2 to be installed in rooms where flueless heating appliances may be fitted. The build up of pollutants to concentrations in excess of the recognised HSE OES and WHO guidelines was not prevented by the purpose-provided ventilation currently required within BS This could be exacerbated as dwellings are made more airtight to meet the increasingly strict requirements of the Building Regulations, unless other ventilation provisions in homes (windows, fans, passive stacks etc.), as required under the Building Regulations are also used in practice. This work was jointly funded by the Health and Safety Executive (HSE) and the Department for Trade and Industry (DTI), but the opinions and conclusions expressed in this report are those of the authors alone and do not necessarily reflect HSE or DTI policy. vi

8 CONTENTS 1. INTRODUCTION 1 2. TEST CHAMBER, APPLIANCES AND EMISSION MONITORING TEST CHAMBER APPLIANCES TESTED MEASUREMENT EQUIPMENT TEST METHODOLOGY 7 3. STANDARDS FOR POLLUTANTS AND EXPOSURES INORGANIC GASEOUS POLLUTANTS ULTRAFINE PARTICLES ALDEHYDES 9 4. RESULTS - CLOSED STOVE STANDARD TESTS TESTS WITH CATALYST REMOVED TESTS AFTER SERVICING TESTS WITH PILOT LIGHT ONLY RESULTS - DECORATIVE FIRE STANDARD TESTS TESTS WITH CATALYST REMOVED INITIAL BURN-IN TEST RESULTS - LPG CABINET HEATER RESULTS INSTANT WATER HEATER AFTER 5 MINUTES RUNNING AFTER 30 MINUTES RUNNING RESULTS GAS COOKER OVEN GRILL HOBS ALONE HOBS WITH PANS OF WATER RESULTS OF ALDEHYDE MEASUREMENTS GENERAL CLOSED STOVE DECORATIVE FIRE CABINET HEATER INSTANT WATER HEATER COOKER EFFECT OF VENTILATION PROVISION BREEZE MODELLING INTRODUCTION EMISSION RATES BREEZE COMPUTER CODE BREEZE MODEL OF FLUELESS APPLIANCE OPERATION 32 vii

9 11.5 BREEZE RESULTS COMPARISON WITH AIR QUALITY STANDARDS AND GUIDELINES CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES TABLES FIGURES 66 viii

10 1. INTRODUCTION There is a long history in the UK of the use of many types of flueless gas appliances, including cookers, instantaneous water heaters, fires and LPG cabinet heaters. BRE analysis of data from the English House Condition Survey (1991) indicated that portable heaters were used in about 5% of homes, representing about 1 million households. These heaters were typically fuelled by bottled gas (normally butane) or paraffin, the former being the most common. However, recently introduced to the UK is a wide range of fixed flueless gas space heaters that are likely to be attractive as a low cost heating option. There are lower costs associated with these appliances arising from the lack of installation of a flue to conduct the gases produced from combustion to the outside of the building, where they could then disperse into the atmosphere. They are also claimed to have lower running costs, with manufacturers stating a gain in energy efficiency, describing them as 100% efficient as no heat is lost up the chimney. Questions have been raised about the potential for combustion products from these innovative appliances to present a health risk within the dwellings in which they are operating. This has also re-awakened interest in the pollutants emitted from all types of indoor flueless gas appliances. Within the current guidance on ventilation provision for this type of appliance (BS ) a certain amount of purpose provided open-area ventilation is specified for rooms likely to house them. The recommendation within Part L1 of the Building Regulations (2002), that unwanted air leakage in buildings should be reduced, should result in new properties having significantly less background ventilation as they are built more airtight. In January 2002, the Health and Safety Executive (HSE) and the Department of Trade and Industry (DTI) commissioned BRE to investigate the concentrations of combustion products likely to result within rooms from a range of flueless gas appliances including: x a closed stove; x a decorative fire; x a cabinet heater; x an instantaneous water heater; and x a cooker. To investigate the pollutant concentration, full-scale measurements were carried out in a controlled chamber and a numerical model (BREEZE simulations) representing a typical house was used to predict the effect of altering various parameters. Parameters investigated in the model included: x pollutant emission rate; x house airtightness; x additional ventilation provision; x internal doors in the house open/closed; x winter and autumn/spring temperature differences between the indoor and outdoor air; and x effects of wind direction. In the absence of UK indoor air quality guidelines, the concentrations of combustion products emitted have been compared with the World Health Organisation (WHO) guidelines and HSE Occupational Exposure Standards (OES). 1

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12 2. TEST CHAMBER, APPLIANCES AND EMISSION MONITORING 2.1 TEST CHAMBER Construction The test chamber was constructed within an existing building, using stainless steel sheeting, with all of the joints between panels being taped and sealed to prevent air leakage. The chamber had a volume of 48 m 3. This ensured that it was in excess of the minimum room volume specified within BS for the installation of this type of appliance (40 m 3 ). The dimensions of the test chamber were: x length = 5 m; x width = 4 m; and x height = 2.4 m. Figure 1 shows two of the appliances within the test chamber, prior to testing Ventilation Fresh air from outside of the building was mechanically supplied to the building housing the test chamber. This ensured that the whole area was properly supplied with fresh air from outside and any combustion products escaping from the vents in the chamber were quickly ventilated away. Two methods of providing ventilation within the chamber were used, purpose-provided openarea and mechanical ventilation. The first method used was to provide the specified open-area ventilation by simply cutting a hole in the walls of the chamber. Installation of purposeprovided open-area ventilation is all that is normally specified with the instructions supplied with the appliances so that they meet the requirements of BS Normally the amount of purpose-provided open-area ventilation that is specified for a room of this size is 100 cm 2, although for one of the appliances tested here, only 50 cm 2 was specified by the manufacturer. Accordingly, open-area ventilation of either 50 or 100 cm 2 was provided in the test chamber, in line with the manufacturer s recommendations for the specific appliance under test. With little or no leakage out of the chamber in the purpose-provided open-area ventilated experiments, it may well be that the vents installed will be ineffective, as the air has no pathways through which to flow out. Also, as the test chamber was housed within another building, the vents would experience lower temperature differences than might be expected to occur between the chamber and outdoors. They would also not be subject to wind-driven pressure effects. As such, these are worst case experiments which would only simulate emissions from appliances into extremely airtight rooms. The second method of ventilation used in the chamber was a controlled mechanical system. Variable speed fans were installed into supply and extract ducting fitted to the chamber so that the air-exchange rate could be set to any desired value. Typically, fixed air change rates of either 0.5 or 1 air changes per hour (ach) were used in the tests with mechanical ventilation. All of the supply air to the chamber was drawn from outside the building. The air extracted from the chamber containing the combustion products was discharged to a different location outside. Air change rates in the chamber were verified by measuring the volume flow rates of air into and 3

13 out of the chamber at the inlet and outlet grilles, using a Flow Finder model 153 balanced volume flow meter. The inlet air supply grille to the chamber can be seen in Figure 1. During experiments with the purpose-provided open-area ventilation, the mechanical ventilation system fans were turned off and the grilles within the chamber were sealed over. Similarly, in the mechanically ventilated tests, any purpose-provided open-areas were sealed over. This ensured that the planned s of ventilation were provided within the chamber during each of the tests. For some of the tests on the water heater and cooker there was no purpose-provided ventilation in the chamber at all, as none is required to be installed within BS for a room of this size in an existing dwelling. However, it should be noted that, under Part F of the Building Regulations, any new dwellings are required to have extract ventilation in their kitchens Air mixing and heat removal A chilled beam with a large fan was installed in the chamber to control the chamber temperature and to ensure good mixing of the air and combustion products from the appliances under test. Chilled water was passed through the beam so that excess heat produced by the gas appliances during the tests could be removed from the chamber. The fan was used to draw air through the porous section of the beam for cooling, and also ensured that the air within the chamber was well mixed. The controller on the chiller unit was set to introduce cold water into the beam so that the room was normally kept at around 23qC or below. The fan drawing air through the beam and mixing the air within the chamber ran continuously during all tests. The chilled beam can be seen in the upper part of the photograph of the chamber (Figure 1). 2.2 APPLIANCES TESTED Closed Stove The closed stove tested ran on natural gas, see Figure 2. It consists of gas burners operating below some decorative logs. The main burners can be controlled from a dial containing numbered settings ranging from 1 to 7. It has a pilot light that in normal use would probably be operated continuously. The unit tested was an ex-display model in good working order. It was initially tested as received. Later in the measurement programme it was fully cleaned and serviced by a CORGI registered gas engineer. Some of the tests were then repeated to see if any differences could be detected. The combustion gases exit through the top of the appliance after passing through a catalyst to remove carbon monoxide (CO). The catalyst is in the form of a ceramic honeycomb block through which the exhaust gas stream is passed. The appliance contains a safety device which constantly monitors the oxygen in the room, if this should fall by as little as 1.5%, the flame is automatically extinguished Decorative Fire The decorative fire tested ran on natural gas, see Figure 3. It consists of gas burners operating below some decorative coals. The main burners can be controlled from a dial containing numbered settings ranging from 1 to 6. It has a pilot light that in normal use would probably be operated continuously. The appliance was bought in new for the purposes of these tests. 4

14 The combustion gases exit through the top of the appliance after passing through a catalyst to remove CO. The catalyst is in the form of a ceramic honeycomb block through which the exhaust gas stream is passed. According to the manufacturer, the appliance contains: a combustion monitoring safety device (ODS). If this operates, the user is advised to: switch the appliance OFF and call in your installer to check the appliance and ventilation Cabinet heater The cabinet heater tested ran on bottled LPG, see Figure 4. The gas is burned directly on ceramic panels. The appliance has three ceramic panels. All three panels are used when the heater is on the high setting, with only one being used on the low setting. The appliance was bought in new for the purposes of these tests. The appliance contains an oxygen analyser and automatic pilot-light cut-off system safety device Instant Water Heater The instant water heater tested ran on natural gas, see Figure 5. It consists of gas burners operating below a heat exchanger through which water is passed, the combustion gases then exit through the top of the appliance. The burner can be controlled from a dial containing settings ranging from low to maximum power. It has a pilot light that would probably normally be operated continuously. The appliance was bought in new for the purposes of these tests. These appliances are specified by the manufacturers as: intended for intermittent use to supply hot water to one draw off point such as a kitchen sink or a wash basin. Within the instructions supplied with the unit tested it states that such appliances: must not be operated continuously for more than five minutes. The appliance contains a safety device which: when the oxygen in the atmosphere in the locality of the heater becomes diminished..interrupts the thermoelectric circuit and the pilot and main burner are extinguished Gas cooker The gas cooker tested ran on natural gas, see Figure 6. It consists of an oven, four hobs of different sizes and a high grill. All ignition was through a piezo-electric system, so no pilot light was used. Although the appliance was not new, it had been used comparatively little, having been purchased new for a previous series of experiments at BRE. 2.3 MEASUREMENT EQUIPMENT A photograph of the gas analysers, data logger and PC described in the following sections is given in Figure Temperature Temperatures were measured at three heights at the centre of the chamber, the supply air entry to the chamber and at the outlet to the appliance under test. Type K thermocouples were used, connected to a Solartron SI 3535D Scorpio data logger. This has its own internal cold junction 5

15 thermocouple reference. Temperature measurements were logged every 10 seconds and recorded on a PC. Measurements were made at five locations, numbered T 1 to T 5 respectively: x T 1 thermocouple positioned at 0.5 m height near the centre of the chamber; x T 2 thermocouple positioned at 1.1 m height near the centre of the chamber; x T 3 thermocouple positioned at 1.6 m height near the centre of the chamber; x T 4 thermocouple positioned at the air supply to the chamber (either at the purposeprovided open-area hole or inlet air supply grille, depending on the nature of the ventilation used in the test); and x T 5 thermocouple positioned in the exhaust stream of the appliance under test Relative humidity Relative humidity was measured using a Vaisala HMP44 probe positioned at a height of 1.1 m at the centre of the chamber. As with the thermocouples, this was logged every 10 seconds via the Scorpio data logger, with values then recorded on the PC Oxides of Nitrogen (NO x ) Measurements were made of nitric oxide (NO), nitrogen dioxide (NO 2 ) and total oxides of nitrogen (NO x ). They were measured using a Thermo-Environment chemi-luminescent analyser, with the entry to the analyser inlet tube being positioned at a height of 1.1 m, near to the centre of the chamber. The calibrated output from the analyser was logged every 10 seconds via the Scorpio data logger, with values then recorded on the PC. The calibration of the instrument was checked on at least a weekly basis using both zero air and span gas from bottled calibration gas standards Carbon Monoxide (CO) CO was measured using a Thermo-Environment infra-red absorption based CO analyser, with the entry to the analyser inlet tube being positioned at a height of 1.1 m, near to the centre of the chamber. The calibrated output from the analyser was logged every 10 seconds via the Scorpio data logger, with values then recorded on the PC. The calibration of the instrument was checked on at least a weekly basis using both zero air and span gas from bottled calibration gas standards Carbon Dioxide (CO 2 ) CO 2 was measured using a Leybold Binos 1 analyser, with the entry to the analyser inlet tube being positioned at a height of 1.1 m, near to the centre of the chamber. The instrument operates by measuring the absorption of infra-red radiation by CO 2. The calibrated output from the analyser was logged every 10 seconds via the Scorpio data logger, with values then recorded on the PC. The calibration of the instrument was checked on at least a weekly basis using both zero air and span gas from bottled calibration gas standards Oxygen concentration The oxygen concentration was measured within the test chamber to see if it declined during the tests as the appliances were operating. The measurement was made at a height of 1.1 m, near to the centre of the test chamber. As a reference, the oxygen outside of the chamber was also measured simultaneously. The measurements were made using electrochemical cells supplied by City Technology (Model numbers 7OX). The calibrated outputs from these cells were logged every 10 seconds via the Scorpio data logger, with values then recorded on the PC. 6

16 2.3.7 Ultrafine particles Measurements of the concentration of ultrafine particles within the chamber were made during most of the tests reported here. The exceptions were the longer, overnight tests as the instrument used would only operate for a period of about 6 hours. The instrument used was a P-Trak particle counter made by TSI Inc. The measurement was made at a height of 1.1 m, near to the centre of the test chamber. The instrument counts the particles present within the air in the approximate size range of 0.02 to 1 Pm. Particles of this size are typically formed as the products of combustion. They are counted rather than weighed, as their small size makes their mass almost negligible Aldehydes Samples of aldehydes were taken during selected tests, covering all of the appliances tested. The samples were collected by pumping known quantities of air through analytical cartridges containing an adsorbent material specifically used for collecting aldehydes. These were then subsequently analysed chemically through a combination of high performance liquid chromatography (HPLC) with UV detection. During the tests, the measurement equipment was stationed at a height of 1.1 m, near to the centre of the test chamber Measurement of fuel used during tests The amount of fuel used was recorded for every test. This acted as a secondary check on the burn-rate of the appliance, as at low firing rates the appliances could sometimes cycle thermostatically, giving lower emissions of pollutants into the chamber than otherwise might have been expected. An in-line gas meter was used for measuring the amount of fuel used in the tests using natural gas from the main supply. This was read before and after each test and the amount of gas used (in litres) recorded. The resolution of the gas meter used was to 0.1 litres. For the tests using the cabinet heater, the cylinder of gas was weighed before and after each test and the amount of gas used (in grams) recorded. The resolution of the balance used was to 0.1 g. 2.4 TEST METHODOLOGY Burn rates and ventilation Tests on all of the appliances were conducted at both high and low burn rates. Ventilation provision was via one of the two methods described earlier in Section (either purposeprovided open-area or controlled mechanical ventilation). For some of the tests on the water heater and cooker there was no purpose provided ventilation in the chamber at all, as none is required to be installed within BS for a room of this size in an existing dwelling. However, it should be noted that, under Part F of the Building Regulations, any new dwellings are required to have extract ventilation in their kitchens Test Periods Tests were normally operated for each appliance type for standard periods. The exceptions were tests where the appliance shut down automatically during the course of the tests. Tests on the room heating appliances (closed stove, decorative fire and the cabinet heater) were typically conducted for periods of four hours. Tests on the oven of the cooker were also typically of four hours duration. 7

17 However, some tests were conducted on the oven at a low burn rate for much longer periods (overnight). These longer period tests were conducted as it is quite possible that an oven could be used for such periods at a lower burn rate, either for slow-cooking of food, or possibly for background heating, for example in a kitchen or bedsit (although strictly this would constitute a misuse of the appliance). Tests on the emissions from pilot lights within some of the appliances were also conducted overnight so that data from a longer period of time could be collected. Measurements of the emissions from the hobs and grill of the cooker were conducted over test periods of 30 minutes, as these would be broadly typical of operating times often used during this type of cooking. Measurements of the emissions from the water heater were conducted over test periods of 30 minutes. Although the heater is specified not to run for period of more than 5 minutes (see Section 2.2.4), there is nothing to stop an operator from running it for periods in excess of this figure. Therefore, the tests were run for 30 minutes, with concentrations of pollutants also being reported after 5 minutes of operation as well Standard Test Procedure In a standard test the procedure was as follows: x install the required appliance within the chamber; x read the gas meter or weigh the gas cylinder as appropriate; x set up the required ventilation condition (open area or mechanical air change rate); x turn on the circulation fan and chilled beam; x start all of the analytical equipment logging to obtain background readings; x light the appliance and seal the chamber door; x at the end of the test period shut down the appliance, leaving the analytical system logging for a few minutes; x read the gas meter or weigh the gas cylinder as appropriate; x shut down the logging system and save all results to disc; x ventilate the chamber completely, prior to any subsequent test. The test procedure minimised the amount of time that an operator needed to be inside the chamber at the end of the testing period. As an additional safety precaution, chamber concentrations of combustion products were checked before entering. 8

18 3. STANDARDS FOR POLLUTANTS AND EXPOSURES The results obtained from the tests were compared with the following standards and guideline concentrations for air quality and exposure: the UK Health and Safety Executive s Occupational Exposure Limits (HSE EH40 (2001)) and the World Health Organisation Air Quality Guidelines (WHO (1999)). The HSE OELs are designed for the workplace, where the working population is assumed to be fit and healthy. These are normally quoted as Occupational Exposure Standards (OES), a time weighted average concentration not to be exceeded, usually over an 8-hour working period, or a short-term exposure limit (STEL) covering a maximum exposure in any 15 minute period. In the absence of any published UK indoor air quality standards, the WHO guidelines were used. The WHO guidelines are set at a lower than the HSE OEL s and are generally taken as being more relevant to the population in general, which encompasses elderly and sick people as well as infants. In terms of potential exposures within homes arising from the emissions from flueless appliances, the WHO guideline concentrations are therefore more appropriate to use as a reference for comparison. 3.1 INORGANIC GASEOUS POLLUTANTS Tables 1 to 4 contain guideline concentrations (where they exist) from both the HSE OELs and the WHO Air Quality Guidelines for the gaseous pollutants measured in these tests (CO, CO 2, NO, NO 2 ). 3.2 ULTRAFINE PARTICLES Currently there are no standards concerning exposure s to ultrafine particles. They were included in the measurements made here as the information gained may be useful in understanding how concentrations of these particles can change as a result of unvented gas combustion. Ultrafine particles were included in the measurements made here, as they are typically generated by combustion processes. 3.3 ALDEHYDES Guideline concentrations for formaldehyde (methanal) and acetaldehyde (ethanal) taken from the World Health Organisation (WHO) are given in Table 5. Aldehydes can cause sensory irritation of the eyes and respiratory symptoms. 9

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20 4. RESULTS - CLOSED STOVE The results of the tests conducted on the closed stove are shown in Table 6, with some examples given in Figures 8 and STANDARD TESTS The measured concentrations of combustion products varied broadly in line with the burning and ventilation rates used in the experiments, with higher burn rates and lower ventilation rates leading to higher pollutant concentrations. The maximum NO 2 concentrations recorded during the tests on this appliance were typically between approximately 50 and 600 ppb, with most of the concentrations being above the WHO 1-hour mean guideline concentration of 105 ppb. Maximum measured concentrations of CO 2 recorded during the tests on this appliance were typically between approximately 800 and ppm. The maximum CO 2 concentrations reached in the chamber during the maximum burn rate tests were always above the HSE s 8 hour OES concentration of 5000 ppm, whereas those from the tests at the lower burn rates were below this concentration. Maximum measured concentrations of CO recorded during the tests on this appliance were typically between approximately 2 and 48 ppm. The maximum concentrations recorded during the higher burn rate tests were always much lower (around 3 ppm) than those at the lower burn rates (up to 48 ppm). At the higher burn rate the maximum concentrations of CO reached were well below the HSE s 8-hour OES concentration of 30 ppm, and the WHO 1-hour mean guideline concentration of 26 ppm. However, at the low burn rates both of these concentrations were often exceeded. Subsequent tests showed that majority of the emissions of CO was being produced by the pilot light of the appliance, see Section 4.4. Lowering of oxygen s within the chamber depended on burn and ventilation rates and varied between reductions of 0.2 and 2.1% of normal atmospheric s in absolute terms. The internal safety device of the appliance automatically shut it down during all of the tests conducted where purpose-provided open area ventilation was used. 4.2 TESTS WITH CATALYST REMOVED Two tests were conducted on the closed stove with the catalyst block removed. The catalysts have a nominal service life specified by the manufacturers of around 10 years, after which it is recommended that they are replaced. Removing the catalyst allowed an evaluation to be made on both the effect that it was having during normal operation, and also the effect that any degradation over time or removal might have on pollutant emissions. The tests were conducted at maximum and minimum burn rates, at a room ventilation rate of 1 air change per hour (ach). It was clear that the catalyst had a significant effect in converting CO to CO 2, as during the maximum burn rate test without the catalyst, the CO concentration in the room reached 50 ppm, compared with a value of only 3.8 ppm in the corresponding test with it in place. Similarly, for the tests at the minimum burn rate, the CO concentration in the room 11

21 reached 39.6 ppm, compared with a value of only 2.2 ppm in the corresponding test with it in place. The catalyst block also affected the balance between the NO and NO 2 emitted into the chamber. For the tests with the catalyst present there was approximately 5 to 8 times more NO emitted than NO 2. However, with the catalyst removed at the higher burn rate there was at least 10 times more NO 2 emitted than NO. 4.3 TESTS AFTER SERVICING The appliance was tested as received from the supplier. It had been in use previously for demonstrations in a showroom. The servicing revealed that the appliance was clean and working properly, but the supply pressure to the pilot light was set at too high a. This was adjusted to be within the manufacturer s specified values. Maximum recorded NO 2 concentrations at the maximum and low burn rates were 130 and 540 ppb before servicing and 150 and 420 ppb after servicing, showing that servicing had had only a small effect on the NO 2 concentrations being produced. Maximum measured concentrations of CO 2 at the maximum and low burn rates were 3700 and ppm before servicing and 3500 and 8600 ppm after servicing, showing that servicing had had a small effect on the CO 2 concentrations being produced. Maximum measured concentrations of CO at the maximum and low burn rates were 3.8 and 48 ppm before servicing and 2.1 and 15.6 ppm after servicing, showing that servicing had reduced CO emissions at the lower burn rate. This lower CO concentration is likely to have arisen from reduced emissions from the pilot light, see Section TESTS WITH PILOT LIGHT ONLY During some of the early tests at the low burn rate, the appliance reached the pre-set desired room temperature (according to the setting on the control dial) and then dropped back to pilot light only operation. This operation was part of the normal thermostatic cycling of the appliance on achieving the desired room temperature (i.e. these were not automatic shut-downs resulting from the intervention of the internal safety device). It was during these periods that higher CO emissions were recorded. It therefore seemed likely that much of the CO being emitted from the appliance was coming from the pilot light. This was probably being compounded by the reduction in the efficiency of the catalytic block once the outlet gas temperature from the appliance fell, leading to higher emissions of CO into the room. To investigate if the pilot light really was the source of the CO emissions, some tests were conducted with just the pilot light running, see Figure 9. During these tests the pilot light was left running for several hours overnight, with the room being ventilated at a rate of 1 air change per hour. In these tests, the concentrations of the other main gaseous pollutants (CO 2 and NO x ) rose slightly from their original background concentrations. However, the concentrations of CO increased more significantly. Prior to servicing, the maximum CO concentration reached in the chamber after running a test overnight was 46.5 ppm. For the final 8 hours of the test the concentration of CO was steady at around 45 ppm, indicating that the HSE 8-hour OES concentration of 30 ppm would have been exceeded. After servicing a similar test produced a of 15.6 ppm, showing that the reduction in pilot jet pressure had reduced CO emissions. During servicing a small sooty deposit on the decorative log that had been positioned next to the pilot light was noticed. To investigate this, a test was run with just the pilot light operating but 12

22 this time with all of the decorative logs removed. The resulting CO concentration in the room with the appliance in this configuration was only 1.1 ppm. The results from the tests on the pilot light alone indicate that potentially it can be a major source of CO. When the appliance is running properly, with higher temperatures within the catalyst block, the catalyst is capable of converting much of the CO produced to CO 2. However, at lower burn rates, much less of the CO is converted to CO 2 and is therefore emitted into the room. Reducing the pilot light supply pressure to within the correct specifications lowered but did not eliminate CO emissions. The design of the decorative logs used within the appliance was such that it was difficult to prevent the pilot light flame from playing on to them. Once the pilot light flame contacted the decorative logs its combustion efficiency was reduced and higher concentrations of CO were produced. 13

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24 5. RESULTS - DECORATIVE FIRE The results of the tests conducted on the decorative fire are shown in Table 7, with an example given in Figure STANDARD TESTS The measured concentrations of the pollutants emitted varied broadly in line with the burning and ventilation rates used in the experiments, with higher burn rates and lower ventilation rates leading to higher pollutant concentrations. The maximum NO 2 concentrations recorded during the tests on this appliance were typically between approximately 300 and 1500 ppb, i.e. always higher than the WHO 1-hour mean guideline concentration of 105 ppb. Maximum measured concentrations of CO 2 recorded during the tests on this appliance were typically between approximately 2000 and 9500 ppm. The maximum CO 2 concentrations reached in the chamber during the higher burn rate tests were always above the HSE s 8-hour OES concentration of 5000 ppm, whereas those from the tests at the lower burn rates were below this concentration. Maximum measured concentrations of CO recorded during the tests on this appliance were typically between approximately 0.5 and 4 ppm. These concentrations being below the HSE s 8 hour OES concentration of 30 ppm, and the WHO 1-hour mean guideline concentration of 26 ppm. Lowering of oxygen s within the chamber depended on burn and ventilation rates and varied between reductions of 0 and 1.6% of normal atmospheric s in absolute terms. The internal safety device of the appliance automatically shut it down during the tests conducted at the maximum burn rate with the minimum room ventilation. 5.2 TESTS WITH CATALYST REMOVED Two tests were conducted on the decorative fire with the catalyst block removed. The catalysts have a nominal service life specified by the manufacturers of around 10 years, after which it is recommended that they are replaced. Removing the catalyst allowed an evaluation to be made on both the effect that it was having during normal operation, and also the effect that any degradation over time or removal might have on pollutant emissions. The tests were conducted at the maximum and minimum burn rates at a room ventilation rate of 1 air change per hour (ach). It was clear that the catalyst had a significant effect in converting CO to CO 2, as during the maximum burn rate test without the catalyst, the CO concentration in the room reached 124 ppm, compared with a concentration of only 3.9 ppm in the corresponding test with it in place. Similarly, for the tests at the minimum burn rate, the concentration of CO in the room for the test without the catalyst was higher, but not by such a large amount. The catalyst block also affected the balance between the NO and NO 2 emitted into the chamber. For the tests with the catalyst present there was approximately 2 to 3 times more NO emitted than NO 2. However, with the catalyst removed at the higher burn rate there was about 3 times 15

25 more NO 2 emitted than NO, whereas at the lower burn rate the two pollutants were approximately equally divided. 5.3 INITIAL BURN-IN TEST The fire was brand new when obtained. The manufacturer s instructions recommend that On initial lightup of a new appliance, the newness will very quickly burn off within the first 5 minutes of operation.the room should be well ventilated with all windows and doors open during this period. Therefore, a burn-in test was conducted to investigate any differences in pollutant emission between a new appliance and one that had been in operation for some time. During the initial burn-in test, it can be seen that s of CO 2 and NO production were similar, as was the reduction in room oxygen. However, higher s of both CO and ultrafine particles were recorded. 16

26 6. RESULTS - LPG CABINET HEATER The results of the tests conducted on the cabinet heater are shown in Table 8, with an example given in Figure 11. The measured concentrations of the pollutants emitted varied broadly in line with the burning and ventilation rates used in the experiments, with higher burn rates and lower ventilation rates leading to higher pollutant concentrations. The appliance produced very little NO, with most of the NO x produced being in the form of NO 2. The maximum NO 2 concentrations recorded during the tests on this appliance were typically between approximately 300 and 900 ppb, i.e. always higher than the WHO 1-hour mean guideline concentration of 105 ppb. Maximum measured concentrations of CO 2 recorded during the tests on this appliance were typically between approximately 4000 and 9500 ppm. These concentrations were close to, or above the HSE s 8-hour OES concentration of 5000 ppm. Maximum measured concentrations of CO recorded during the tests on this appliance were typically between approximately 7 and 17 ppm. These concentrations were below the HSE s 8 hour OES concentration of 30 ppm, and the WHO 1-hour mean guideline concentration of 26 ppm. However, they were very close to, or above the WHO 8-hour mean guideline concentration of 9 ppm. Lowering of oxygen s within the chamber depended on burn and ventilation rates and varied between reductions of 0.2 and 1.4% of normal atmospheric s in absolute terms. The internal safety device of the appliance automatically shut it down during all of the maximum burn rate tests and also during the low burn rate at the minimum ventilation condition. 17