The Storage of Flammable Liquids in School Laboratories

Transcription

1 The Storage of Flammable Liquids in School Laboratories From June 1993 issue of Crucible Volume 24.3 INTRODUCTION This article provides some recommendations for: storing flammable liquids; the quantities to be kept in schools; the types of storage cabinets usable; and the need to vent those cabinets. Such venting would neither violate the Ontario Fire Code, nor compromise the ULC standards, but would help to ensure the health and safety of teachers and lab technicians involved. FLAMMABLE LIQUIDS IN LABS The recommendations regarding the quantities and storage of flammable liquids in labs are based on the "National Fire Protection Association (NFPA) standard 45" which has as its objective the offering of standard guidelines in the prevention and control of fires and explosions in laboratories, and for handling and storage of hazardous chemicals. The recommendation to vent these cabinets is based on the need for an atmosphere that does not endanger the safety and health of the teachers as required by Regulation 692/80 made under the Health and Safety Act of Ontario. Quantities Flammable liquids, by their nature, present three hazards : a health hazard, a fire hazard from the presence of open fire sources as small as sparks, and a possible explosion hazard if their vapour/air mixture reaches its lower explosive limit inside the non-vented cabinet. R.R.O. 692/80, limits the quantities in Industrial Establishments stored in a metal cabinet to 235L. For practical reasons in high schools, it is recommended that quantities for no more than one year s consumption, dated on receipt, be stored. The more the hazards of a liquid, the less the quantities that should be on hand. These liquids do not only present a problem in storage and use, but also in disposal of surpluses, or products of reactions. The less the frequency of use of a flammable liquid, the smaller should be the quantity to be stored. The NFPA recommendations on the quantities to be stored in educational institutions depend, among other criteria, on whether the liquids are COMBUSTIBLE or FLAMMABLE. The differentiation depends on their flash points. Flash Point: The minimum temperature at which a liquid gives off vapour in sufficient concentration to form an ignitable mixture with air near the surface of the liquid under specified conditions of testing.

2 Combustible Liquid: A liquid having flash point above 37.8 C. Flammable Liquid: A liquid having flash point below 37.8 C, and having a vapour pressure not exceeding kpa at the above temperature. Container type and size The NFPA recommends the maximum allowable size of Containers depends on the class of liquid: Flammable Liquids o CLASS IA : liquids having flash points below 22.8 C, and boiling point below 37.8 C. o CLASS IB : liquids having flash points below 22.8 C, and boiling point above 37.8 C. o CLASS IC : liquids having flash points at or above 22.8 C, and below 37.8 C. Combustible Liquids o CLASS II : liquids having flash points at or above 37.8 C, and below 60 C. o CLASS IIIA : liquids having flash points at or above 60 C, and below 93.4 C. o CLASS IIIB : liquids having flash points above 93.4 C. The above classification of Classes IA to IIIA is adopted by the Ontario Fire Code, proposed Part 4. The following table shows the maximum allowable container capacity. Flammable liquids Combustible liquids Container class class class class class Size A IB IC II IIIA Glass* 0.5 L 1 L 4 L 4 L 4 L Metal or approved 4 L 20 L 20 L 20 L 20 L plastic Safety cans** 8 L 20 L 20 L 20 L 20 L * Class IA and Class IB flammable liquids in glass containers larger than 0.5 L or 1 L sizes should be stored in metal pails, or other suitable containers of sufficient size to hold the liquids in the glass container. The NFPA recommends that these cans must be provided with a pressure-releasing mechanism that will safely relieve internal pressure when subjected to fire exposure, and should be of not more than 23 litres (5 gallons) capacity and must not break if dropped. **R.R.O. 692/80 states that a portable container used for dispensing flammable liquid in a work area shall be made of material suitable to provide for the safety of all workers and have, a) a spring-loaded cap; and b) a flame arrestor. The red plastic containers for carrying car gasoline are not suitable.

3 Waste from the use of flammable liquids solvents should be treated as the flammable liquids themselves. STORAGE ANFPA Standard # 45 recommends that the storage cabinet for flammable and combustible liquids be constructed in accordance with the requirements set forth in ANFPA standard 30 : Flammable and combustible Liquids Code. Since there are no regulations under the Occupational Health and Safety Act for Educational Institutions, Regulation 692/80 for Industrial Establishments has been used as a guide. These regulations cover the storage of flammable liquids, and states that a maximum of 235 L may be stored in a metal cabinet of double walled construction, with a 3-point door latch and a liquid-tight door sill raised at least fifty millimetres above the floor. The proposed Part 4 of the Ontario Fire Code also states the specifications for their construction. The construction of such cabinets and the fire testing are covered by the American National Standard ANSI/UL standard # , and the Canadian UL standard #C , and CAN4- S101-M. VENTILATION OF FLAMMABLE LIQUIDS STORAGE CABINETS Ventilation is indirectly required by the Health and Safety Act Regulations R.R.O. 692/80 which stipulates that the employer must supply the workers with an atmosphere that does not endanger their health and safety, i.e. clean of hazardous chemicals. Those teachers who have unvented cabinets, may be exposed to a high level of toxic fumes when the non-vented cabinet is opened. It also states that the discharge of air from any exhaust system shall be in such a manner so as to prevent the return of contaminate to any work place. The vapours out of an unvented cabinet would certainly circulate in the workplace before being sucked out, even if one have proper ventilation of the prep room. Ventilation is required for the health and safety of students and teachers In the CRC Handbook of Laboratory Safety, it is stated clearly that most flammable liquids are toxic in some degree and require ventilation to safe-guard the health of the operators. The publication "Safety in Science Laboratories" by the Department of Education and Science in England states that it should be remembered that flammable liquids generate vapours which are explosive when mixed with air. Some of the vapours are also toxic. Ventilation is required to reduce the hazard of an explosion. In the CRC Handbook of Laboratory Safety, it is stated clearly that ventilation that is safe from a health standpoint, will usually be more than adequate to overcome any explosion hazard. Such explosion hazard exists if the flammable vapour/air ratio in the non-vented cabinet reaches its lower explosive limit.

4 FISHER-EMD 89/90 catalogue states that two fire-baffled outlets can be unplugged and connected to a lab exhaust system...to prevent accumulation of hazardous vapours. Ventilation of the cabinets will neither destroy the integrity of the CSA and ULC rating, nor violate the Ontario Building Code. a) The CSA does not yet have standards for the Flammable Liquids Cabinets. b) The ULC standard # C1275/1984, does not state anywhere that venting the cabinets will affect their rating. The scope of the standard is to determine the ability of the cabinets to withstand a standard fire exposure for a period of ten minutes, without developing an internal rise in excess of 139 C above ambient. Scientifically speaking, venting the cabinet (to the outside we recommend), will keep the outside air (at least as warm as ambient) circulating through the cabinet, and thus reducing its internal temperature, as well as diluting the flammable vapours. This cabinet is to protect its content from being EXPOSED to an outside fire. The opinion of the ULC when contacted, was to go ahead and vent them, venting has nothing to do with the warranty or liability. c) The National Fire Code of Canada, 1990, does not prohibit venting. d) The National Fire Protection Association in the USA, which is a recognized authority, states in its Code 30: "Storage cabinets shall be designed and constructed to limit the internal temperature... when subjected to... a room fire exposure...the cabinet is not required to be vented, for fire protection purposes; however the following shall apply: If the cabinet is vented for other reasons, the cabinet shall be vented outdoors in such a manner that will not compromise the specified performance of the cabinet, as acceptable to the authority having jurisdiction. If the cabinet is not vented, the vent opening shall be sealed with a properly fitted metal bung". Also, it states: "Venting storage cabinets has not been demonstrated to be necessary for fire protection purposes. Additionally, venting a cabinet could compromise the ability of the cabinet to adequately protect its contents from involvement in a fire since cabinets are not generally tested with any venting. Therefore, venting of storage cabinets is not recommended. However, it is recognized that some jurisdictions may require storage cabinets to be vented and that venting may also be desirable for other reasons, such as health and safety. In such cases, the venting system should be installed so as to not affect substantially the desired performance of the cabinet during a fire..." Then it continues, stating the way and standards to be followed in venting.

5 As teachers, we are concerned about health and safety as well as fire hazards. Material possessions can be replaced, but human life and health could never be compensated for. Also, the recommendation not to vent them for fire protection reasons is based on the fact that cabinets are not generally tested with any venting as stated above. It is quite reasonable to say that venting, and having a cold air return from the outside, will keep the inside of the cabinets cooler than its outside in a fire, and thus prevents the temperature of the cabinet s centre from rising above the stipulated temperature of C. Here we see the term "VENT OPENING", which indicates the purpose of these openings on the sides of cabinet. e) Catalogues of such cabinets manufacturers and distributors state as a feature, the provision of vents, as seen in the following catalogues: LEVITT-SAFETY LIMITED, CATALOGUE-50 which states "...in addition, they are shipped with capped vents so that vents can remain closed or be opened". WILLIAMS CORPORATION OF QUALITY SAFETY PRODUCTS "...2 inch threaded vents, one on each side, allow for ventilation". The EAGLE MANUFACTURING COMPANY flyer states "...both vents, with a 2 inch thread fitting, have fire baffle and cap..." on these cabinets. f) The Ontario Fire Code,1987, in its proposed 1989, draft of Part 4, states that "unless approved, where a cabinet referred to in Article is provided with cabinet ventilation, the vents shall terminate outside the building in accordance with article ". This means that the Ontario Fire Code does not prohibit venting such cabinets. Authorities recommending the ventilation of the flammables storage cabinets a) In the article "How To Store Hazardous Chemicals" by Glen & Sterling, published in the Occupational Health and Safety Canada, they state that "...Storage cabinets can be used to house small quantities of flammable material...the cabinets should be properly labelled and vented..." and "flammable liquids... ventilation should prevent contamination of inside storage areas..." b) The National Research Council (USA) in its book on "Prudent Practices for Handling Hazardous Chemicals in Laboratories" (1981), states "...small quantities of flammable liquids should be stored in ventilated storage cabinets..." c) The National Research Council (USA) in its periodical "Occupational Health Nursing" July- August 1988 issue, in the article on Flammable Liquids Storage and Handling Safety Tips, states that "...commercial cabinets provide a connection for venting that should be used when possible". d) R.B. Scott, in an article in the Journal of Chemical Education on the "Control of Hazards in the Laboratory", states that "volatile and corrosive substances for general lab use should be stored in ventilated cabinets".

6 Construction of Venting System It should be noted that components of mechanical venting should be fire rated and motors be spark proof. For further requirements, check with the Ontario Fire Code,1987, in its proposed 1989 draft of Part 4. Types of Cabinet Ventilation There are two types of cabinet ventilation: passive or gravity venting, and mechanical active venting. The author strongly recommends active ventilation. Types of Cabinets for Storage of Flammable Liquids The Ontario Fire Code,1987, in its proposed 1989, draft of Part 4, allows the use of specially designed and constructed metal or wood cabinets. RECOMMENDATIONS Based on the material in this article, the author and the STAO Safety Committee recommend that flammable liquids should be stored in limited quantities in proper containers in properly vented ULC approved flammables cabinets.