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## What are the occupational exposure limits for workplace noise?

Occupational exposure limits (OELs) for noise are typically given as the maximum duration of exposure permitted for various noise levels. They are often displayed in exposure-duration tables like Table 1A and Table 1B. The OELs depend on two key factors that are used to prepare exposure-duration tables: the criterion level and the exchange rate.

Table 1A
Noise Exposure Limits when Criterion Level = 90 dB(A)
3 dB(A) Exchange Rate Maximum Permitted
Daily Duration (hours)
5 dB(A) Exchange Rate
Allowable Level dB(A) Allowable Level dB(A)
90 8 90
93 4 95
96 2 100
99 1 105
102 0.5 110
105 0.25 115

Table 1B
Noise Exposure Limits when Criterion Level = 85 dB(A)
3 dB(A) Exchange Rate Maximum Permitted
Daily Duration (hours)
5 dB(A) Exchange Rate
Allowable Level dB(A) Allowable Level dB(A)
85 8 85
88 4 90
91 2 95
94 1 100
97 0.5 105
100 0.25 110

## What is the criterion level?

The criterion level, often abbreviated as Lc, is the steady noise level permitted for a full eight-hour work shift. This is 85 dB(A) in most jurisdictions, but it is 90 dB(A) in Quebec and 87 dB(A) for organizations that follow the Canadian federal noise regulations.

## What is the exchange rate?

As the sound level increases above the criterion level, Lc, the allowed exposure time must be decreased. The allowed maximum exposure time is calculated by using an exchange rate, also called a "dose-trading relation" or "trading ratio." The exchange rate is the amount by which the permitted sound level may increase if the exposure time is halved.

There are two types of exchange rates currently in use: 3 dB(A) exchange rate or the "3 dB rule," and 5 dB(A) exchange rate or the "5 dB rule." These two exchange rates, with criterion levels of 85 dB(A) and 90 dB(A), give two different sets of exposure guidelines, as Table 1A and 1B show.

The 3 dB(A) exchange rate is more stringent. For example, the maximum permitted duration for a 100 dB(A) noise exposure in the 3 dB(A) exchange rate is 15 minutes. With the 5 dB(A) exchange rate, it is one hour.

Most experts recognize the 3 dB rule as more logical. They argue that it is logical that if the sound level is doubled, then the allowable exposure time should be cut in half. It follows, then, that the allowable time should be halved for every 3 dB(A) increase in sound level. This is precisely the case if the 3 dB(A) exchange rate is used.

The table below shows the criterion levels (i.e., maximum permitted exposure levels for 8 hours) and the exchange rates used in different Canadian jurisdictions.

## What are the noise exposure limits in Canadian jurisdictions?

Jurisdiction
(federal, provincial, territorial)
Continuous Noise* Impulse / Impact Noise*
Maximum Permitted
Exposure Level for 8 Hours: dB(A)
Exchange Rate
dB(A) +
Maximum Peak Pressure Level
dB(peak)
Maximum Number of Impacts
Canada (Federal) 87 3 - -
British Columbia 85 3 140 -
Alberta 85 3 - -
Manitoba 85 3 - -
Ontario 85 3 - -
Quebec 90 5 140 100
New Brunswick 85 3 140 -
Nova Scotia 85 3 - -
Prince Edward Island 85 3 - -
Newfoundland and Labrador 85 3 - -
Northwest Territories 85 5 140 100
Nunavut 85 3 or 5** 140 -
Yukon Territories 85 3 140 90

+ When 3 dB exchange rate is used, generally there is no separate regulation for impulse/impact noise. The equivalent sound exposure level (Lex) takes impulse noise into account in the same way as it does that for continuous or intermittent noise.

** In Nunavut, the General Safety Regulations reference a 5 dBA exchange rate. The Mining Health and Safety Regulations reference 3 dBA. Please contact Nunavut for further information.

Noise regulations in several jurisdictions treat impulse noise separately from continuous noise. A common approach is to limit the number of impulses at a given peak pressure over a workday. The exact figures vary slightly, but generally the regulations in which the exchange rate is 5 dB permit 10,000 impulses at a peak pressure level of 120 dB; 1,000 impulses at 130 dB; 100 impulses at 140 dB, and none above 140 dB.

Alternatively, using a 3 dB(A) exchange rate, impulse noise can be considered jointly with any continuous noise, in measuring the overall Leq sound level.

## Where do you find noise exposure limits in Canadian legislation?

The following are references to the federal, provincial, and territorial legislation where you will find the occupational noise exposure limits from the different jurisdictions in Canada. Since legislation is amended from time to time, the jurisdiction should be contacted for the most current information about the noise exposure limits and how they are enforced. This information is intended as a guide only and may not apply to specific occupational sectors (for example, mining). The regulations should also be consulted for information on requirements for hearing protective equipment and other control measures that may be prescribed for protecting the hearing of workers. Please contact your local office of the occupational health and safety agency for your jurisdiction if you have specific questions that apply to your workplace.

Canada Labour Code, Part II, (R.S.C. 1985, c. L-2)
Canada Occupational Safety and Health Regulations, (SOR/86-304)
Section 7.4(1)(b)

### British Columbia

Worker's Compensation Act
Occupational Health and Safety Regulations (BC Reg 296/97 as amended)
Section 7.2 [B.C. Reg. 382/2004, s.1]

### Alberta

Occupational Health and Safety Code, 2009
Section 218; Table 1 of Schedule 3

Occupational Health and Safety Act, 1993 [R.R.S. c.0-1.1, r.1]
Occupational Health and Safety Regulations, 1996
Part VIII, Section 113 (1)

### Manitoba

Workplace Safety and Health Act [R.S.M. 1987, c. W210]
Workplace Safety and Health Regulation (Man. Reg. 217/2006) Part 12

### Ontario

Occupational Health and Safety Act [R.S.O. 1990, c.1]
Industrial Establishments (R.R.O. 1990, Reg 851)
Section 139

### Quebec

Act Respecting Occupational Health and Safety [R.S.Q., c.2.1]
Regulation respecting Occupational Health and Safety (O.C.885-2001)
Division XV, Sections 130-141

### New Brunswick

Occupational Health and Safety Act
General Regulation (N.B reg. 91-191 as amended)
Part V, Sections 29 to 33

### Nova Scotia

Workplace Health and Safety Regulations
N.S. Reg. 52/2013
Part 2, Section 2.1 to 2.3
(references ACGIH TLVs, as updated annually)

### Prince Edward Island

Occupational Health and Safety Act
Occupational Health and Safety Act General Regulations (E.C. 180/87)
Part 8, Section 8.3

Occupational Health and Safety Act
Occupational Health and Safety Regulations, 2012
Section 68
(references ACGIH TLV, as updated annually)

### Northwest Territories

Safety Act
General Safety Regulations (RRNWT 1990, c. S-1, R-028-93 as amended)
Section 30 and 31, Schedule A, Table 1

### Nunavut

Safety Act
General Safety Regulations (RRNWT 1990, c. S-1)
Section 30 and 31, Schedule A
Mine Health and Safety Regulations, R-125-95
Section 9.19-9.26, Schedule 5

### Yukon Territories

Occupational Health and Safety Act
Occupational Health Regulation (O.I.C. 1986/164)
Section 4

Document last updated on March 5, 2014

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