Click
on any of the following links for detailed information.
·
OCCUPATIONAL
EXPOSURE LIMITS
Worker exposure to a hazardous substance must not exceed the exposure limit adopted by ACGIH and set out in the 1997 Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. The table below is excerpted from the ACGIH publication, and contains some common hazardous substances and their exposure limits.
|
Chemical name |
8-hour exposure limit |
15-minute exposure limit |
Ceiling |
|
Acetic acid |
10 ppm |
15 ppm |
-- |
|
Acetone |
500 ppm |
750 ppm |
-- |
|
Ammonia |
25 ppm |
35 ppm |
-- |
|
Carbon black |
3.5 mg/m3 |
-- |
-- |
|
Carbon dioxide |
5,000 ppm |
30,000 ppm |
-- |
|
Carbon monoxide |
25 ppm |
-- |
-- |
|
Ethyl acetate |
400 ppm |
-- |
-- |
|
Formaldehyde |
-- |
-- |
0.3 ppm |
|
Hydrogen sulfide |
10 ppm |
15 ppm |
-- |
|
Hydroquinone |
2 mg/m3 |
-- |
-- |
|
Isopropyl alcohol |
400 ppm |
500 ppm |
-- |
|
Sulfur dioxide |
2 ppm |
5 ppm |
-- |
If a worker is exposed to a contaminant other than during an eight-hour day and a forty-hour week, the employer must use the Brief and Scala model to adjust the threshold limit values. The Brief and Scala model is found on page 10 of the ACGIH publication.
The employer must ensure there is appropriate medical surveillance of employees exposed to air contaminants for at least 12 months after the threshold limit values for the contaminants have been adjusted according to the Brief and Scala method. (General Regulation 91-191, 21, 24.1)
Where the employer or an employee has reason to believe that an air contaminant may exceed 50 percent of the threshold limit value, the employer must test the air to determine the level of the contaminant. (General Regulation 91-191, 24)
The employer must ensure that the workplace is adequately ventilated. Ventilation can be natural if it is provided by openings having a combined area of at least 5 percent of the floor space. Mechanical ventilation must conform to ASHRAE 62-1989 Ventilation for Acceptable Indoor Air Quality. (General Regulation 91-191, 20)
Where the installation of engineering controls is practical, the employer must install and use them to keep employee exposure below the threshold limit values. (General Regulation 91-191, 24)
Local exhaust
Where practical, air contaminants must be removed at their source. (General Regulation 91-191, 20)
If the ASHRAE standard does not specify the amount of make-up air, the employer must ensure it is at least 8 litres per second per employee.
The employer must ensure that the make-up air does not contain exhausted air.
The employer must ensure that make-up air is not hazardous to workers, does not contain contaminants at a concentration greater than 10 percent of the exposure limit, is heated as necessary and does not create drafts. (General Regulation 91-191, 20)
Continue by clicking any item
on the menu bar on the left.