Alert C19: Application of Waterproof Coatings in Rooms and Confined Spaces

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Ontario Ministry of Labour

Summary Statement

Workers have been injured or died as a result of preparing or spraying waterproof coatings in rooms or confined spaces. Discusses OSHA regulations and steps to take to improve safety.
Feb 2000

Alert C19: ISSN 1195-5228
Produced by the Construction Health and Safety Program
Issued: February 2000

Hazard Summary:

Two workers have died and four have been critically injured as a result of preparing or spraying waterproof coatings in rooms or confined spaces. In all cases, the spray operators were self-employed and used portable spray equipment in trailers or trucks. These incidents occurred over the past four years.

Waterproofing products contain toluene and heptane that are toxic by inhalation and extremely flammable. The process requires stringent controls to prevent and protect against hazardous levels of contaminants.


Construction projects and industrial establishments where a waterproofing application is required.

This hazard occurs during the spraying application or cleaning of equipment used to apply the waterproof coatings where inadequate ventilation and a source of ignition are present.

Legal Requirements and Precautions:

  • The Occupational Health and Safety Act (the Act) applies.
    Section 25(2)(h) states that: "an employer shall take every precaution reasonable in the circumstances for the protection of the worker."

    Precautions include (but are not limited to) training, safe handling and storage of flammable liquids and work in confined spaces.

  • The Workplace Hazardous Materials Information System (WHMIS) Regulation, R.R.O. 1990, Reg. 860, also applies with respect to training, labels and Material Safety Data Sheets (MSDS).

    The Regulations for Construction Projects made under the Act (O. Reg. 213/91) sections 43 and 58 about use and storage of flammable liquids, sections 52 to 57 about fire safety and sections 60 to 63 about confined space entry also apply.

  1. Safe work procedures must be prepared and reviewed prior to spraying or application in a room or confined space. Workers shall receive adequate training and instruction in safe work procedures and in the use of respiratory protective equipment.
  2. Operators must be fully trained in WHMIS equipment and procedures involving confined spaces.
  3. All sources of ignition, particularly static electricity, must be eliminated or disconnected or removed. All equipment must be properly grounded and explosion proof.
  4. The room or confined space must have adequate ventilation. The operation must NOT be carried out in unventilated areas.
  5. Appropriate personal protective equipment must be worn.
  6. Confined space requirements must be followed where applicable. Requirements include:
    • Entry by operators working alone is strictly prohibited. Operations involving confined spaces require a minimum of two persons plus an emergency procedure for rescue.
    • Entry is permitted if it is certified as safe by a competent worker or if:
      • the worker wears suitable breathing apparatus,
      • the worker wears a full body harness, securely attached to a rope, with the free end tied to a fixed support outside the confined space,
      • the worker outside the confined space is equipped with an alarm,
      • a means of communication between the worker in the confined space and the worker outside is provided,
      • a person trained in artificial respiration and equipped and able to perform rescue operations is readily available,
      • all equipment is inspected by a competent worker who confirms it is in working order.
  7. Spray operations are prohibited if the concentration of vapour in the air exceeds 10% of the Lower Explosive Limit (LEL), i.e., 1000 ppm if the LEL is 1% vol/vol. Entry into confined spaces is not permitted if the concentration of flammable vapours exceeds 50% of the LEL. The work locations must be evaluated by a competent person before work in a confined space is attempted.
  8. This value will almost certainly be exceeded in unventilated areas, or where ventilation is poor or uncertain. The operation must not be attempted unless adequate mechanical exhaust ventilation is provided.
  9. Since high vapour concentrations are likely from the spray operation, the operator must wear a self-contained breathing apparatus, or an air supplied respirator.
  10. Continuous monitoring of the level of flammable vapours is encouraged.

Remember that while complying with occupational health and safety laws, you are also required to comply with applicable environmental laws.

Please photocopy Ministry of Labour Alerts, distribute them widely and post them where people will see them