The National Fire Prevention Association, NFPA, does not recommend venting a chemical storage cabinet and it is not required by OSHA. However, local authorities have the final word. Knowing this, storage cabinet manufacturers often include capped venting bungs for users who are required to vent by:

• State or local codes
• Their insurance carrier
• Their own company

 If venting is done, it is recommended that it be connected to an existing exhaust such as a fume hood, which is designed to handle corrosive vapors. Flame arrestors do not need to be used and PVC is the best material for venting corrosives. Chemical storage cabinets for flammables, corrosives or pesticides/poisons often come with capped bung openings for venting. However, some cabinets made from wood or polyethylene are not provided with bungs for venting. When purchasing safety storage cabinets, check to see if there are vents if you know this is a requirement in your area.

Follow local guidelines for venting the safety storage cabinet and at the very minimum, include these steps:

• Remove both metal bungs from the sides of the cabinet and place the flame arrester screens in the openings. Usually, these screens come with the cabinet.
• Connect the bottom opening to the exhaust fan using rigid metal tubing equivalent or better than that used in the cabinet construction.
• Exhaust vent materials for hazardous material cabinet should be compatible with the cabinet’s contents.
• Vent materials for flammable liquid storage cabinet must be resistant to high temperatures in case of fire.
• Stainless steel, hard-soldered copper and carbon steel are all appropriate vent materials for flammable storage cabinets.
• The tubing must have an inner diameter no less than that of the opening. You might be required to weld the tubing to the cabinet to avoid riveting or using other methods that may compromise the cabinet’s fire protection.
• The specified performance of the UL listing of the cabinet must not be compromised.
• The top opening serves as the fresh air inlet. Make-up air should be supplied to the fresh air inlet in tubing like that used for the exhaust.
• A fan should be constructed of non-sparking blades and shrouds. Mechanical exhaust ventilation is preferred and should also comply with NFPA 91, Standard For Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Non-compatible Particulate Solids.

The local authority which requires venting should be consulted for engineering guidance to be certain their protocol is followed. These guidelines are specific for flammable liquid storage cabinets but they can be modified for corrosive/acids or pesticides/poison storage cabinets.

Important Points To Remember

• The total run of the exhaust should not exceed 25 feet.
• DO NOT manifold vents of multiple cabinets. This is prohibited in many areas.
• PVC pipe should not be used to vent a flammable liquid storage cabinet as it could melt in case of fire.
• Some authorities recommend the use of PVC pipe instead of metal with some types of storage cabinets. Check with your local jurisdiction about this.
• Polypropylene is combustible and should not be used in venting.
• Corrosive cabinets must have blowers that are chemically compatible with the vapors they will move.
• Some pesticide/poison cabinets can not be vented to the outside due to potential health hazards from exposure to the vapors.