Safety – To Vent or not to Vent Flammables Cabinets

Question to STAO Safety Committee:

I was at a school that had an externally vented flammable cabinet.  The cabinet at my current school isn’t vented and there is always a strong (somewhat overpowering) smell whenever the cabinet is opened.  While the MSDS sheet for methanol recommends use in a vented area, the storage requirements are only the use of a flammable cabinet.

I had the board’s safety officer to the site and he questioned the purchase of larger containers (1 L sizes) of alcohols and the presence of a large metal 10 L ethanol container.  He said the problem was with an overly filled cabinet and suggested that we dispose of our chemicals and just buy smaller quantities.  I tried to argue that this really doesn’t change the VOC nature of the chemicals.

Does STAO recommend the use of a vented flammable cabinet?


The advice from your safety officer is consistent with the STAO policy regarding the storage of chemicals. In our document Safe ON Science (2011), it is suggested that chemical inventories be reduced to include only those chemicals that are required. These should be purchased in quantities that can be consumed within a two to three year time frame. In our archives (Crucible 1994) in an article on flammable cabinet ventilation, the following sound advice was given:

For practical reasons in high schools, it is recommended that  (flammable liquids) 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.

As time goes on, the caps and sealer inserts become compromised and the liquids evaporate contributing to the vapours that come out of the  cabinet when it is opened. Ordering fresh new chemicals in smaller quantities regularly, while more expensive, reduces the  accumulated vapours. Removing chemicals that are seldom, if ever, used can also reduce the vaporous content of the flammables cabinet.

The National Research Council, in their book Prudent Practices in the Laboratory (published 2011 pp 239,240), has described two view points:

One view is that all such cabinets should be vented by using an approved exhaust system, because it reduces the concentration of flammable vapours below the LEL inside the cabinet. No fuel will be rich enough in vapour to support combustion. The other view is that in most circumstances flammable-liquid storage cabinets should not be ventilated. With a source of fuel and fresh air in vented cabinets, all that is needed is ignition for a fire to be started. Both views are valid.

VIEW ONE: In addition to reducing chemical inventories, and the quantities of chemicals stored, STAO does recommend the use of vented flammable cabinets. This reduces the exposure of teachers to vapours in the chemical storage area. For this reason, there also should not be any work stations or offices in this area.

VIEW TWO: The Ministry of Education (email received 2014), in compliance with Ontario Fire Code, requires that each school develop its own fire safety plan. This plan has to have the approval of local fire department officials. Local fire department officials approve ventilated cabinets in some districts, and do not approve them in others. Example: In my particular district, the ventilation of cabinets is not approved as it can cause a chimney effect during a fire.

Requirements for installing venting:

The National Fire Protection Agency is an international agency. In 2014, Ontario will adopt the NFPA Professional Qualification Standards at the request of the Ontario Fire Marshal Office.

NFPA code 30 Section 9.5 (2015)

There is no requirement of exhaust ventilation for storage cabinets, although most have plugged fittings for that purpose. Exhaust should only be provided when warranted by the materials in the cabinet (toxic or noxious materials). The manufacturer’s instructions must be followed if exhaust ventilation is installed. Typically,this will involve small diameter steel duct or pipe leading directly and by the shortest route to the exterior of the building. Exhaust must be taken from the bottom of the cabinet.

Next Steps:

  • Follow the advice of your safety officer by reducing your inventory of flammable liquids and reducing the quantities that you are storing. Resolve to order smaller quantities more often. Do this in consultation with your department members.
  • If the vapours continue to be problematic, then contact your local fire department to see if they have objections to ventilation of a flammable liquids storage cabinet.
  • If the local fire department has no objections then prepare a summary sheet of the steps you have taken, and the information you have gathered. Suggest a solution to the problem in your summary sheet. Including a price quote will likely expedite the matter. Request a meeting with your joint Health and Safety Committee and your School Board Safety Officer.

We hope that the information provided in this response will be helpful in your making an informed decision. If you have any new information as regards vented flammable cabinets, please share that with our committee. We also request feedback as to the clarity, speed, and thoroughness of our response. This will allow us to improve this service. Please do not hesitate to ask any safety questions by sending them to

David Gervais

Chair of STAO Safety Committee