High-Impact Health & Safety Support Services

The Old Rules

For many years, section 139 of the Industrial Regulations, under the Occupational Health & Safety Act, specified a “criterion (maximum) level” of 90 dBA (decibels on the “A” weighting network, measured with the “slow” response setting on a “Type 2” sound level meter). This meant that a worker could have exposure to noise of up to 90 dBA for 8 hours without the worker being required to wear any hearing protection or the employer being required to take action to reduce exposures.

Further, the “exchange rate” (or doubling rate) was 5 dBA, which meant that a worker could be exposed to 4 hours at 95 dBA, or 2 hours at 100 dBA (and so on, to higher levels up to a maximum of 115 dBA) without the worker having to wear hearing protection or the employer being obligated to reduce workplace noise. If a worker’s exposure exceeded the above limits, the employer was required to take unspecified “measures” to reduce the sound level below 90 dBA. Where such measures were “not practicable”, the employer was required to restrict exposure durations (to a maximum of 90 dBA for 8 hours, 95 dBA for 4 hours, and so on) or to provide, and enforce the wearing of, hearing protection.

Warning signs at approaches to areas where noise levels exceeded 90 dBA were required to be posted, stating the level of noise and the daily limit for that noise level (for example: 95 dBA, 4 hours daily limit), and that hearing protection must be worn when the daily exposure was exceeded. The hearing protection in use was required to be capable of reducing the worker’s noise exposure to below 90 dBA for an 8‐hour shift.

The Law has Changed

Effective in 2007, regulation 139 was significantly amended - the first major change in 30 years. It now specifies a much lower “criterion" level of 85 dBA (decibels on the “A” weighting network, measured with the “slow” response setting of a “Type 2” integrating sound level meter, to give an estimate of “equivalent sound exposure level”, or Lex.8). This means that a worker can have a Lex.8 exposure of only 85 (not 90) dBA for 8 hours without being required to wear hearing protection, and without the employer being required to reduce worker exposures to noise. Hearing protection is recommended, however, by the Ontario Ministry of Labour, for exposures above a Lex.8 of 80 dBA.

This drop in the allowed exposure, since noise is on a logarithmic scale, amounts to a cut of close to 75% in the allowed noise exposure! It is not often that workplace exposure limits are slashed to that extent, in "one fell swoop".

Further, the “exchange rate” has now been lowered to 3 (not 5) dBA, which means that a worker can be exposed to up to 4 hours at only 88 (not 95) dBA, or up to 2 hours at only 91 (not 100) dBA (and so on) without having to wear hearing protection, provided his Lex.8 is 85 dBA or less for the 8‐hour shift. As you can see, these exposure limits have been drastically reduced (because the decibel scale is logarithmic, a drop of only 3 decibels cuts the noise level in half). Requirements on employers to reduce workplace noise now "kicks in" at much lower noise levels.

If a worker’s exposure to noise exceeds the above reduced limits, the employer is now required to take “all measures reasonably necessary in the circumstances” to “protect workers from exposure to hazardous sound levels”. The “protective measures” are specified as “engineering controls (see footnote 1 below), work practices (footnote 2 below) and, subject to subsection 7 of regulation 139, personal protective equipment (or hearing protection). If hearing protection is used, it is now required to be capable of reducing the worker’s noise exposure to below 85 (not 90) dBA for an 8‐hour shift.

Subsection 7 of Regulation 139 lists only certain situations where an employer can resort to providing and enforcing the use of hearing protectors: where engineering controls

• Do not exist, or cannot be obtained;
• Are not reasonable or practical; or
• Have been installed but are temporarily out of service, or are ineffective due to some emergency.

This amended provincial regulation (and similar provisions in Part VII of the Occupational Health and Safety Regulations under the Canada Labour Code) puts the onus on employers to investigate various engineering controls to determine if any are reasonable and practical to implement, and arrange for installation, unless they are found to be impractical or unreasonable, rather than to simply depend on a hearing protection program. If any are not able to be implemented, the employer should keep all documentation to show the Ministry of Labour (or federal) officer, should this information be requested at a later date. If no evidence of the employer’s investigation into the feasibility of engineering controls can be produced, the officer has the power to order that engineering controls be
investigated.

Warning signs at approaches to areas where noise levels exceed 85 (not 90) dBA are still required to be posted (however, old signs will likely need to be replaced and relocated).

(1) For noise, engineering controls include such measures as selecting quieter equipment; reducing machine speed, fluid flow velocity and/ or fluid pressure; preventive maintenance; equipment vibration isolation; application of vibration damping materials to vibrating surfaces; sealing openings, if feasible; mufflers for noisy gas discharges; equipment enclosures, barrier screens or shields; acoustically-shielded operating booths; application of sound-absorbing material to walls, floors and ceilings; increasing the distance from the worker to the noise source; and
custom‐designed active noise cancellation systems.

(2) Also called “administrative controls” these include measures taken to reduce workers’ exposure times to noise (for example, exposing two workers for half the 8‐hour shift to 88 dBA, instead of one worker to that level for a full 8‐hour shift – both workers’ Lex,8 would still have to be 85 dBA or less).

If you have any questions regarding this information, please feel free to contact

Larry Westlake, P.Eng.

High-Impact Health & Safety Support Services

Phone: (807) 345-6691

Email: ohslaw@shaw.ca