EXPLOSION HAZARDS IN DISPENSING PRODUCTS CONTAINING TOLUENE

Produced by:
Professional and Specialized Services,
Ontario Ministry of Labour
Alert #16/0296
ISSN 1195-5228 

HAZARD SUMMARY 

Toluene is a flammable liquid with a flash point of 4.4 degrees 
Celcius.  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.

REQUIRE PRECAUTIONS

Section 63 of the Regulations for Industrial Establishments (RRO 
851/90) 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)):

a)  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. 

b)  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.) 

c)  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 24(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 Ontario 
             Hydro as safe for use in hazardous areas.  During 
             their pre-development review of the operation, 
             Ministry of Labour industrial engineers assign the 
             appropriate Electrical Safety Code classification to 
             hazardous areas. 

d)  The area must have provision for explosion venting.

e)  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:

a)  mechanical ventilation from floor level to the outdoors at 
    the rate of eighteen cubic metres per hour per square metre 
    of floor area; and 

b)  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 (O.Reg. 860/90 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 (MSDS) 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  Heatings for Areas Containing Flammable or Explosive Gases, 
      Vapours, Dust or Fumes 
10-0  Static Electricity 

For assistance, contact your nearest Ministry of Labour office.