Safety Office Reviewed: Dec 2013 Reviewed: DD Month Year Guidance on safe use of Autoclaves 1. Hazards & Uses There are several different types of hazard associated with the use of autoclaves. The main ones are associated with: Exposure to steam under pressure. Contact with hot surfaces and liquids Failure of the pressure vessel itself Manual handling whilst loading and unloading Exposure to infectious substances within the load Failure of the makesafe/discard cycle to sterilise contaminated waste. Autoclaves are used to sterilise equipment, media and to inactivate waste and therefore it is vitally important that sterility is assured. The following describes some of the main factors that should be taken into account in risk assessments, the types of control measures to be implemented and provides information on the key requirements for ensuring effective sterilisation. 2. Choice and performance The relevant British Standard covering use of autoclaves in laboratories is BS 2646 Autoclaves for Sterilisation in Laboratories 1993 and BSEN 12347: 1998 Performance criteria for steam sterilisers and autoclaves. When Schools are purchasing autoclaves or arranging maintenance work they should always check that the autoclave and the associated installation and servicing complies with the British Standard specifications. The need for any additional controls such as HEPA filters on the exhaust for autoclaves in Containment Level 3 laboratories should be determined by risk assessment. 3. Maintenance & Validation Regular maintenance is essential for the continued efficiency and safety of laboratory autoclaves and ancillary equipment. Schools should have a continuing programme of planned preventative maintenance throughout the life of the autoclave, in accordance with the manufactures recommendations. Where the autoclave is used to make safe waste it is also necessary to validate and monitor the performance of the autoclave. Further details on this are given in section 14 below. 4. Periodic examination In addition to ongoing maintenance and validation arrangements, it is a requirement under the Pressure Systems Safety Regulations that autoclaves be periodically examined by a competent person. This examination is necessary prior to the autoclave being brought in to service and thereafter at appropriate regular intervals. Within the University this is carried out by the University's Engineering Insurers Notification In order to ensure these requirements are met the details of all autoclaves must be notified at the time of installation or purchase to the Responsible Person within the
School, who will arrange for them to be added to the insurer s database, in order that they are assessed, insured and regularly inspected. The procedure for this can be found on the Commercial Services Website (follow the links to Insurance; Engineering and Statutory Inspections; Standard Inspections for Pressure Vessels and Lifting Equipment). The Safety Office should also be notified about autoclaves that are to be used for biological/gm waste inactivation so that appropriate checks can been made of validation procedures. These notification requirements also apply to any autoclave that is relocated within the University. 5. Management, Information and Training Autoclaves should be under the managerial control of a nominated individual who will be the responsible person for ensuring that the autoclave is safely managed and operated by trained and competent individuals. Operation instructions should be provided for the operator and should include details of action to be taken by the operator in the event of a fault or any abnormality in autoclave performance. It is recommended that simple, easy to understand instructions are provided close to the equipment. This should be drawn up with reference to the manual provided by the manufacturer. The responsible person /manager of the facility must ensure that operators receive training in accordance with the written instructions and are deemed competent before being allowed to operate the autoclave. Training and attainment of competence must be noted in the individuals training record. There should also be a notice adjacent to the autoclave which shows the name of the responsible person and a list of people trained and authorised to use the equipment. 6. Routine Inspection & Maintenance by Operators In addition to the maintenance and inspection detailed above there are a series of routine checks that should be carried out by the responsible person or a nominated individual. After each run the chart recorder should be inspected to ascertain that the operating cycle has been achieved. The following procedure should be carried out after each operation or where autoclaves are in constant use, at a suitable interval [minimum weekly]. When performing these tasks ensure that the autoclave is in a cool and safe condition Clean the chamber internally including fittings, shelves and brackets, as recommended by the manufacturer. Clean the drain filter if fitted. Clean the door seal with a damp cloth and examine to ensure there are no cuts or abrasions. Weekly Check the operation of indicator lamps. During an operating cycle, check the pressure gauge against the temperature gauge to ensure correct operation.
7. Failure during the discard cycle When a fault occurs during a discard/makesafe cycle an assessment of risk should be made and appropriate action taken. It may be necessary to disinfect those chamber attachments on which engineering work is to be carried out. During a makesafe process, chamber condensate should be considered to be contaminated with viable microorganisms. Therefore adequate time must be allowed to allow the autoclave to cool down completely and for aerosol to dissipate before opening the door. A contaminated laboratory autoclave should never be returned to the manufacturer for servicing or repair. Decontamination should be carried out in accordance with local safety rules before a service engineer works on the autoclave and suitable decontamination certification provided. The use of permit to work systems for routine maintenance by service engineers is strongly recommended. 8. Protective Clothing & Equipment Protective clothing with long cuffed sleeves worn in the autoclave loading/unloading area(s). Additional protective clothing should be available in the loading/unloading area(s) to protect the operator. This should include: An impervious apron Heatresistant gauntlet gloves A fullface visor Suitable nonslip heavyduty safety shoes 9. Loading the Autoclave The hazards on loading include spills of biohazardous material, broken glass and dropped load contents. Controls All materials awaiting autoclaving should be stored safely. Bagged waste materials should be supported in a robust, leakproof container, bags should never be placed directly on the floor. It should be possible to identify the source of all materials to be autoclaved. A labelling system should be used in order that the waste can be tracked back to the laboratory or area from where it came. This serves two important purposes. Firstly to be able to identify the contents of the waste and what hazards may be present in the event of someone having an accident in which they are exposed to any infectious agents that may be present. Secondly to be able to identify the producer of the waste if there is any problem with it, such as a container is leaking, overfilled, or contains inappropriate items etc., to prevent repetition of bad practice. Items should be packed in a way that ensures that steam will penetrate the load. Bags should not be sealed; if the tops have been taped or tied the bags should be opened or slashed to allow effective steam penetration. The following tin has been specifically designed to facilitate safe transport and ensure effective steam penetration and it is strongly recommended that these be used wherever possible.
For discard/waste inactivation, the load within the autoclave must be positioned in accordance with the load validation arrangements outlined in Appendix A and the validation report [see section 13]. Ensure that the volume of liquid in the vessel containing the reference probe is at the correct level as detailed in the validation report. When some chemicals (including disinfectants) or materials are autoclaved they are likely to produce vapours that could harm persons exposed when opening the door or they may be corrosive [e.g. Virkon or Chloros] to the autoclave. A risk assessment should be made of all items to be autoclaved taking account of this possibility. Radioactive waste must not be autoclaved. It must be sealed in a yellow burn bin and sent for incineration. If the waste is genetically modified it will need to go to an incinerator registered to accept GM Waste, if it cannot be effectively inactivated by disinfection. Consult the Safety Office for advice. 10. Unloading the Autoclave The hazards on unloading include splashes and spillage of hot material from the load, hot condensate, hot equipment, broken glass, dropped load contents, and vapour from volatile chemicals. Controls Temperature and pressure indicators and warning lights should be checked to ensure that the autoclave has successfully completed the operating cycle. If a fault is indicated, attempts to open the autoclave should only be made with the authority of the responsible person. It is dangerous to attempt to release the autoclave door mechanism before the chamber is vented to atmosphere or whilst the load contents are at high temperature. No attempt should be made by the operator to override door interlocking safety devices. The operator should stand clear when opening the door as hot liquid or vapour may escape from the chamber. The operator should also be aware that containers of liquid could be pressurised and may explode, volatile liquids may produce harmful vapour and liquids spilled on unloading may cause scalding. The following measures are designed to minimise the unloading hazard: temperature activated door interlocks; timer activated door interlocks; training and supervision of operators; protective clothing; and load transfer systems.
After autoclaving, waste containers should be emptied in a safe manner and their contents disposed of or reclaimed as specified by local laboratory rules. IN the event of there being a breakage inside the autoclave ensure that cut resistant gloves are worn and there is some means of removing debris from the rear of the chamber [e.g. long tongs/litter picker] 11. Waste Containers All waste should be placed in waste containers which should be easily transportable, leak proof and of a robust design with solid sides and bottoms. They should allow adequate steam penetration to the contents. If autoclave plastic bags are used they should be supported in a waste container whilst in the laboratory, during transport to the autoclave and also whilst in the autoclave. The bag should be open during the autoclave cycle so that steam can penetrate its contents. It is recommended that transparent (rather than opaque) autoclave bags be used as this allows the autoclave operator to see if any hazardous materials have been placed in the bag by mistake. 12. Operating Cycles Typical operating cycle conditions are listed in the table below. TYPICAL OPERATING CYCLE CONDITIONS Process Sterilising Temperature 0 C Holding Time (Minutes) Min 0 C Max 0 C Min Max Liquids sterilisation 121 115 124 118 15 30 Equipment/glassware sterilisation 121 126 134 124 129 138 15 10 3 Makesafe (for inactivation waste) 134 recommended 126 138 130 3 10 The operating cycle should take account of heat up times. The time required for the load to reach sterilizing temperature should be determined during validation tests.
12.1 Operating Cycles for Liquids Sterilisation When liquids are sterilised the possibility of adverse effects on the liquid caused by the heat treatment must also be taken into account on selecting a cycle. The operating cycle should be selected to ensure that sterilisation is achieved with minimum damage to the liquid. Microbiological culture media are particularly heat sensitive; the degree of deterioration is related to the length of time the medium is maintained at sterilising temperature; the heatup and cooling stages also contribute significantly to this deterioration. Heatup times should be as short as possible, achieved by uniformly filling the chamber with steam at sterilising temperature. Large volumes of fluids will heat up slowly, therefore volumes of liquids should be kept small; a maximum container volume of 500ml is recommended, larger volumes taking considerably longer to heat up (and cool down). Cooling loads quickly helps to protect heatsensitive constituents and also shortens operating cycle times. Air at high pressure may be admitted to ballast the chamber, minimise boiling and prevent bottles exploding. Containers should be loosely capped unless they are specifically designed for sealing. However, sealing bottles can increase the likelihood of explosion during autoclaving and slows cooling. 12.2 Operating Cycles for Waste Inactivation When sterilising loads which contain infectious waste it is important that the sterilising temperature is attained and maintained for the required time at the centre of each part of the load. In order to ensure the minimum sterilising temperature at the centre of each part of the load is achieved the air must be completely removed from the load and then steam must then be injected into the chamber at specific pressure in order to ensure it penetrates the load. The temperature must then be held for the required sterilising time. Because contents of a waste inactivation load varies, this holding time may be in excess of the minimum required time this is to ensure that all parts of the load achieve that temperature for the minimum time. Key factors affecting this are: Load materials Plastic and card (consider the release of formaldehyde from card) containers will act as an insulator increasing the equilibration time. Metal boxes are the preferred option. Plastic coated bottles also act as an insulator, taking longer to heat up that normal glass bottles. Load Configuration The validated load must be documented, repeatable and based on a worst case scenario. Ideally validated loads should be photographed and logged on Appendix A.. Any new waste loads will need to be validated before the work commences. Waste should only be loaded and autoclaved in an approved and validated load pattern. Porous Loads Air removal is a key factor, failure to achieve direct steam contact with Dry Saturated Steam can lead to failure, regardless of whether the required temperature was achieved within the load.
A vacuum cycle should be used where possible and when not available a free steam cycle should be set up along with the use of approved discard containers. 13. Validation, Calibration and Routine Monitoring of Autoclave Performance 13.1 Validation & Calibration Validation is testing the ability of the autoclave to effectively perform the autoclaving process when loaded with userdefined loads. An autoclave cycle can be split into three phases, heating up, holding at pressure and cooling down. Validation should demonstrate that in the holding part of the cycle the necessary temperature has been attained throughout the load and this is held for the minimum time. Calibration, which should not be confused with validation, compares the temperature set on the dial to the temperature in the chamber. 13.2 The validation process For discard/make safe cycles where loads contain pathogens or harmful genetically modified microorganisms then validation must demonstrate that the process is effective in achieving a 100% kill. The validated load must be documented, repeatable and based on a worst case scenario, validated loads should be photographed and logged on Appendix A To do this a worst case load of simulated waste (i.e. worst case volumes, materials and equipment but not contaminated with pathogens) should be placed in the autoclave for the validation test.. Any new waste loads will need to be approved and validated before the work commences. Waste should only be loaded and autoclaved in an approved and validated load pattern. Appendix A is a Load Validation Form which can be used to ensure the validation load is suitably set up and recorded. Probes are then inserted at various 12 points in the waste and connected to recording equipment. This then shows the temperature at the various points throughout the cycle. The holding part of the cycle commences once all sensors indicate the prescribed sterilizing temperature has been reached. All sensors must then maintain at least that temperature for the prescribed holding time. Validation must be carried out by a competent trained person using thermometric test equipment that is calibrated and traceable to national standards. The test method is described in British Standard 2646. The use of biological or chemical indicators for this purpose is not acceptable. The use of bench top autoclaves for waste is not recommended because these cannot usually be validated. Loads comprising a variety of items and containers do not heat uniformly. Short holding times are therefore subject to large proportionate variations and should be avoided if possible. Following validation it will be possible to ascertain the settings required on the autoclave to achieve the above conditions. This will vary considerably with many factors including the load characteristics. For example, one particular autoclave may need to be set at 121 o C for 50 minutes in order to achieve cycle (i) above whereas another may need to be set at 123 o C for 75 minutes to achieve the same. Where dials can be altered by the user, the temperature and time requirements for a waste cycle should be clearly displayed on the autoclave.
13.3 The Validation Report The validation report must contain information on the temperature achieved for each probe and the time held along with the location of each probe. This is typically displayed in a table format along with a diagram of the chamber layout. Chamber set up and validation notes Channel Number Location Max Temp Min Temp Holding Time Comments 13.4 Frequency of validation Validation and calibration must be carried out at the frequencies shown below and at any other times when the previous test may no longer be valid (such as part of recommissioning after maintenance work). Waste containing Group 1 & 2 organisms Group 3 organisms at least annually six monthly The person responsible for the autoclave should check certificates and printouts received for the validation testing to satisfy themselves that the autoclave meets the criteria specified above for the required cycle(s). Validation records should be kept for 5 years. These will be inspected during audits by the Safety office and may be requested by Health and Safety Executive Inspectors during visits to the University. 13.5 Routine monitoring by users
Following validation, autoclave performance should be routinely monitored. Where autoclaves are used for waste containing pathogens, the autoclave should be fitted with chart recorders or print out facilities and these should be checked after each run and kept as part of the autoclave process record. Autoclave tape and indicators printed on bags do not show the load has been sterilised. These are used only to indicate that a load has been processed since the stripes appears very quickly even at low temperatures. Use of these would not be regarded as an adequate means of monitoring autoclave performance. Biological indicators are vials containing Geobacillus stearothermophilus which can be used to confirm that sterilisation is achieved. These are not a substitute for validation as described in section 13.1 above but are a useful means of confirming effective sterilisation in between formal validation cycles.
APPENDIX A Load Validation Form Autoclave Name and Serial Number Location Chamber (If applicable) Load Description / Ref Required cycle temperature and time Full Description of load at each point (note points 1 & 2 in are drain and load probe) 1 2 3 4 5 6 7 Photo of load Notes: