During the COVID-19 emergency, the Safety Office is continuing to provide services.

Click here for more information on essential services that will continue, work that will be suspended, the laboratory shutdown checklist, and changes to the ESF hours.

Roofing projects

Roofing repairs and re-roofing of University buildings are of vital importance to stop water damage and mould growth in buildings. This page contains more information on roofing projects at the University. 

Background and health hazards of asphalt

Roofing asphalt is a petroleum-based product. It is not a single chemical, but a mixture containing many different chemicals. During roofing projects, asphalt is heated in roofing kettles which generate odours from fume and vapour emissions. Due to the low odour threshold of the sulfur compounds in asphalt, odours can at times be very strong, resulting in building occupants reporting health symptoms.

Short-term effects

Roofing asphalt fumes and vapours can cause headaches, dizziness, nausea and lung irritation. They may also irritate the skin, eyes, nose and throat. These effects are usually mild and temporary. Although building occupants may experience discomfort, the fumes and vapours generally do not pose a health hazard. Symptoms should resolve within hours after exposure to the odour has ended.

Individuals with medical conditions

However, some individuals with medical conditions, especially respiratory conditions, may have their conditions aggravated by roofing asphalt fumes. These individuals should avoid inhaling roofing asphalt emissions and review with their supervisor any accommodations required in their work schedule or location.

Hydrogen sulfide gas

Hydrogen sulfide is a by-product of the heating process of asphalt. Only levels inside an enclosed roofing kettle may be high enough to pose a serious health threat.

Building occupant exposure

While roofing workers may be exposed to asphalt fume and vapour emissions at a significant level, building occupants should not have significant exposures. In Ontario, the American Conference of Governmental Industrial Hygienists (ACGIH) occupational exposure limit over an 8-hour workday and 40-hour work week has a threshold limit value (TLV) of 0.5 mg/m³(2008). Under this limit, workers exposed are not expected to experience adverse health effects. Building occupant exposure is generally accepted to be significantly below the TLV, even though odours may be strong. Long-term health effects in building occupants are not anticipated. Some studies show a higher incidence of certain cancers in asphalt workers, however, asphalt fume and vapour emissions are not classified as a human carcinogen.


Methods to reduce odours during roofing projects

  1. Procedures are followed by Plant Operations to minimize the infiltration of fumes and vapour emissions into buildings. These include:
    • Using roofing kettles with afterburners
    • Locating roofing kettles away from and downwind of building air intakes
    • Closing and sealing air intakes if the roofing kettle cannot be moved away from air intakes
    • Adjusting building ventilation systems according to roofing activity
    • Selecting appropriate roofing materials
  2. Building occupants should be notified before roofing projects begin. Occupants with known respiratory conditions should consider relocation during roofing activities and should consult their physician if they experience adverse health effects.
  3. Windows downwind from roofing kettles should be kept closed while roofing work is occurring.

Addressing concerns during roofing projects

  • During a building roofing project, resolution of concerns is facilitated by a department/faculty designating a contact person such as an administrative assistant or health and safety coordinator to receive concerns from building occupants. The contact person then addresses concerns directly with Plant Operations.
  • Information about roofing concerns is forwarded to the appropriate Plant Operations construction coordinator. Other persons are not permitted under the Occupational Health and Safety Act and Regulations for construction projects to direct a contractor unless authorized by Plant Operations.
  • If you have immediate concerns relating to roofing projects including:
    • Unusual amounts of fumes/smoke entering the building
    • Unsafe conditions such as blocked exits or construction debris
  • Notify your department/faculty contact person (if designated) or Plant Operations ext. 33793 (24 hr service).
  • If you require further information regarding asphalt materials used in a roofing project, contact the Safety Office at safety@uwaterloo.ca or call ext. 33587, and the project-specific Material Safety Data Sheets (MSDS) can be obtained.
  • If you require an accommodation, notify your supervisor.