Alert: Explosion Hazards in Dispensing Products Containing Toluene

• ISSN: 1195-5228
• Issued: February 1996
• Content last reviewed: June 2009

Hazard Summary:

Toluene is a flammable liquid with a flash point of 4.4° C. Toluene and products containing it can form an explosive mixture with air at room temperature. When these products are dispensed in enclosed and poorly ventilated areas vapours can build up to the point where sparks from electrical equipment, static electricity or open flames can ignite them, causing a fire or explosion or both. Explosions and fires caused in this way have resulted in deaths.

Many precautions must be taken when dispensing toluene or mixtures containing it. These include adequate ventilation, bonding, grounding and protection from sources of ignition.

Locations and Sectors:

The manufacturing, automotive, construction and mining sectors.

Required Precautions:

Section 63 of the Regulations for Industrial Establishments [R.R.O. 1990, Reg. 851] requires that when a process is likely to produce a gas, vapour (e.g., toluene vapour), dust or fume to such an extent as to be capable of forming an explosive mixture with air, the process must be carried out under the following five conditions (subsections (a) through (e)):

1. The area where the process is carried out must be isolated from other operations.

   Note: When flammable liquids such as toluene are dispensed, the process must be carried out in a room or area that is isolated from other operations in the building.

2. The area must have a system of ventilation adequate to ensure that the gas, vapour, dust or fume does not reach hazardous concentration.

   Note: Mechanical ventilation must be provided at a rate capable of reducing the vapour concentration below 25 per cent of the lower explosive limit of the solvent vapour mixture in the air. When practicable, the dispensing process must be interlocked with the ventilation system, so that if the ventilation system is stopped or fails, the dispensing process is also stopped. (See also subsection 22(4), quoted below.)

3. The area must have no potential sources of ignition.

   Note 1: Potential sources of ignition include:

   • open flames
   • smoking
   • hot surfaces
   • electrical sparks
   • static electricity (see also subsection 22(4) quoted below)
   • cutting and welding
   • radiant heat
   • frictional heat or sparks

   Note 2: Electrical installations used in dispensing areas must be inspected on site and approved by the Electrical Safety Authority as safe for use in hazardous areas.

4. The area must have provision for explosion venting.
5. The area must have, where applicable, baffles, chokes or dampers to reduce the effects of any explosion.

Subsection 22(4) of the regulation states that an area where flammable liquids are dispensed must have:

1. mechanical ventilation from floor level to the outdoors at the rate of eighteen cubic metres per hour per square metre of floor area; and
2. containers and dispensing equipment bonded and grounded when flammable liquid is dispensed.

The Ministry of Labour recommends the following precautions for the dispensing of flammable liquids:

• Use pumps or self-closing valves designed in accordance with good engineering practice in the dispensing of flammable liquids.
• When receiving containers have small openings, install flexible metal or conductive rubber hoses on the faucet to reduce spillage. If drums are in the horizontal position for dispensing, use a flame-arrestor bung vent.
• Make sure that workers wear clothing and footwear that dissipate static electrical charges during the dispensing process because man-made fibres and regular footwear generate static.

As required under the WHMIS (Workplace Hazardous Materials Information System) Regulation [R.R.O. 1990, Reg. 860, as amended by O. Reg. 36/93], all containers of hazardous products must be labelled and adequate product-specific training must be provided to workers. The material safety data sheet (September 1, 2011 11:07 for the product should be consulted for information on safe handling.

For More Information

See the following Ministry of Labour Engineering Data Sheets for more information:

• 4-01 Storage and Dispensing of Flammable Liquids
• 5-03 Heating for Areas Containing Flammable or Explosive Gases, Vapours, Dust or Fumes
• 10-0 Static Electricity

For assistance, contact your nearest Ministry of Labour office.