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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 |
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.
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.
| 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 | - | - |
| Saskatchewan | 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** | *** | 140 | 100 |
| Nunavut | 85** | *** | 140 | - |
| Yukon Territories | 85 | 3 | 140 | 90 |
* For more information about continuous, impulse and impact noise, please see Noise - Basic Information.
+ 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 and Northwest Territories, the Occupational Health and Safety Regulations reference a staged action plan based on the dBA exposure level (80, 85, and 90).
*** In both territories, the Mining Health and Safety Regulations reference 3 dBA. Please contact Northwest Territories and/or 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.
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.
