Levels of Sound - Canada Occupational Health and Safety Regulations, Part VII - IPG-074

Effective Date: April 2010

1. Issue

Part VII (Levels of Sound) of the Canada Occupational Health and Safety Regulations .

2. Background

Part VII (Levels of Sound) of the Canada Occupational Health and Safety Regulations, as amended in May 2002, prescribes the maximum duration of exposure of an employee to given sound levels in the work place.

The purpose of this document is to aid concerned parties in the interpretation and implementation of Part VII (Levels of Sound). It is not an in-depth technical document; rather, it is an expansion of selected sections of the regulation.

3. Questions

3.1

What is the relationship between A-weighted Sound Pressure Levels and Noise Exposure Levels?

3.2

How are measurements made and exposure calculated?

3.3

What is involved in a Hazard Investigation?

3.4

What needs to be considered regarding hearing protection?

4. Answers

4.1 Sound Pressure Level and Noise Exposure Section 7.1

Most sound-measuring instruments respond to sound pressure. When all the sound frequencies are treated uniformly (i.e., no particular emphasis is placed on some frequencies over others) we measure sound pressure level, and the unit of measurement is the decibel (abbreviated as dB). If an electronic network known as the "A" weighting network is included in the measurement, we are said to measure A-weighted sound pressure level, and the unit of measurement is called "decibel, A-weighted" (abbreviated as dBA). A-weighted sound pressure level is also commonly referred to as sound level.

Noise exposure level (abbreviated as Lex, 8) refers to the exposure of an employee to sound. It is a measurement which combines the A-weighted sound pressure level to which an employee is exposed with the duration of exposure to that sound level. The mathematical definition of noise exposure level is given in this section. The main points to be noted are: (a) all work place exposure to sound during a continuous 24-hour period is taken into consideration when measuring or calculating the noise exposure level, and (b), the exposure is averaged over 8 hours regardless of the number of hours worked during a 24-hour period. Noise exposure level is usually measured with a noise dosimeter, whereas A-weighted sound pressure level is measured with a sound level meter.

4.2 Measurement and Calculation of Exposure

Subsection 7.2(1) deals with the type of instruments (and their specification) which shall be used to measure the exposure to sound of an employee. It references the appropriate clauses in the Canadian National Standard CAN/CSA Z107.56-M86, Procedures for the Measurement of Occupational Noise Exposure, as amended from time to time.

Subsection 7.2(2) specifies the procedures to be followed for measuring the exposure to sound of an employee. It references the appropriate clauses in the CSA standard cited in 7.2(1).

Subsections 7.2(3) and (4) specify what is known as the "Threshold Level" for noise exposure measurement. This is the lowest sound level which shall be included in the measurement (or calculation) of the noise exposure level of an employee. Subsection 7.2(3) requires that sound levels down to at least 74 dBA shall be included [1] . While it may be possible to program some noise dosimeters for this threshold, it is not a feature common to all dosimeters.

This is recognized in the regulation. The employer is permitted to use a dosimeter even if it cannot be programmed for 74 dBA, as long as it is capable of measuring (and including in the calculation of noise exposure level) sound levels below 74 dBA.

4.3 Hazard Investigation

Section 7.3 requires the employer, under certain conditions, to carry out an investigation in the work place for the purpose of assessing the exposure of employees to sound.

Subsection 7.3(1) provides that where an employee may be exposed to A-weighted sound pressure levels of 84 dBA, or greater, for a period of time likely to damage the employee's hearing, the employer shall initiate an investigation to be made for assessing the exposure. In the interest of health and safety, it is suggested that employers should carry out hazard investigations where there are identifiable sources of noise which produce sound levels of at least 80 to 90 dBA on a regular basis, and to which employees might be exposed.

Paragraphs 7.3(1)(a) and (b) require the employer to appoint a qualified person to conduct an investigation for the purpose of determining the degree of employee exposure to sound in the work place and to notify the work place committee or the health and safety representative of the name of the investigator.

It should be noted that paragraph 135(7)(e) of Part II of the Code stipulates that a work place committee shall participate in all inquiries and investigations pertaining to occupational health and safety. Similar powers are granted to the health and safety representative under paragraph 136(5)(g).

Subsection 7.3(3) prescribes that the measurement of the A-weighted sound pressure level referred to in 7.3(1) shall be performed instantaneously using the slow response setting of a sound level meter. These measurements are required to be made under normal working conditions.

Paragraphs 7.3(4)(a), (b), (c), (d) and (e) specify certain elements which the qualified person must consider when conducting the hazard investigation.

Subsection 7.3(5) states that, on completion of the investigation, and after the qualified person has consulted with the work place committee or the health and safety representative the qualified person shall make a written report, date it and sign it. The intent of this subsection is that the qualified person is made fully aware of the concern of the work place committee or the health and safety representative, and that he or she has taken into consideration any recommendations or suggestions made by the committee/representative. It is not incumbent upon the qualified person to adopt such recommendations or suggestions.

Paragraphs 7.3(5)(a), (b) and (c) require the qualified person to include in the investigation report, observations with respect to paragraphs 7.3(4)(a), (b), (c), (d) and (e). The report must also include recommendations for the purpose of complying with the prescribed sound level limits, the posting of warning signs and the use of hearing protectors. The qualified person may recommend the use of hearing protectors if the noise exposure level is more than 84 dBA and less than 87 dBA. For example, if the employee is exposed to a Lex, 8 of 84 or 85 dBA on an intermittent basis (say one day a week), the qualified person may well decide that hearing protection is not needed. On the other hand, if the exposure persists for 3 or 4 days a week, the qualified person might recommend the use of hearing protection.

Subsection 7.3(6) requires the employer to keep the hazard investigation report at the work place where the investigation was conducted for a period of ten years after the date of the report.

Paragraphs 7.3(7)(a) and (b) prescribe that where the investigation reveals that employees are likely to be exposed to a noise exposure level (Lex, 8) of 84 dBA or greater, the employer shall post, and keep posted, a copy of the report in the work place where the investigation took place, and also provide employees, so exposed, with written information describing the hazards associated with exposure to high sound levels.

The employer may obtain this material from such sources as the Labour Program, the Canadian Centre for Occupational Health and Safety (CCOHS) in Hamilton, or prepare an information package in consultation with the work place committee or the health and safety representative.

Limits of Exposure

Paragraphs 7.4(a) and (b) prescribe limits of exposure of employees to sound in any 24-hour period. Paragraph (a) references the Schedule which sets out the maximum duration of exposure in hours to which an employee can be exposed in a 24-hour period to A-weighted sound pressure levels from 87 dBA to 120 dBA. Paragraph (b) prescribes that the noise exposure level (Lex, 8) of an employee shall not exceed 87 dBA for 8 hours in any 24-hour period.

The following points should be noted:

  • The reference to the 24-hour period is meant to protect those employees who may work more than 8 hours within that time period. For example, if an employee starts his shift at 8 am, ends at 4 pm, then comes back to duty at midnight for another 8-hour shift, that employee shall be considered to have worked for 16 hours within that 24-hour period. In that case, the employee's noise exposure level (Lex, 8) shall not exceed 84 dBA over a 16-hour period (as opposed to the limit of 87 dBA over an 8-hour period).
  • Even though the Schedule starts at an A-weighted sound pressure level of 87 dBA and ends at 120 dBA, it is incumbent upon the employer to take into consideration all noise from at least 74 dBA onwards as per subsections 7.2(3) and (4).

The maximum duration of exposure should be based on the time spent exposed to noise at the work site, regardless of whether or not the individual is on duty. In the Schedule, the exposure duration is decreased by half for every 3 dBA increase in A-weighted sound pressure level.

Report to Regional Health and Safety Officer

Section 7.5 requires the employer to reduce the employee's exposure to sound, without the use of hearing protectors, to the limits specified in section 7.4 where reasonably practicable, by engineering or other physical controls, or by administrative controls such as reducing the length of exposure.

An Interpretation Policy Guideline (920-I-IPG-055) is available which expands on the criteria for "reasonably practicable".

Paragraphs 7.6(a) and (b) state that the employer must, without delay, report in writing to a regional health and safety officer where it is not reasonably practicable to maintain the exposure to sound of employees at or below the limits specified in 7.4, without providing hearing protectors. Paragraph 7.6(a) requires the employer to report in writing to the regional health and safety officer the reasons why exposures cannot be maintained below the prescribed limits. Subsection 7.6(b) requires the employer to provide a copy of the report to the work place committee or the health and safety representative, if any.

Possible justifications for not reducing the sound levels are outlined in IPG-055. The regional health and safety officer cannot "accept" or "reject" the report but may use it as a basis to decide whether further investigation is required by the Labour Program.

4.4 Hearing Protection

Paragraphs 7.7(1)(a) and (b) prescribe that when an employer is required to make a report to a regional health and safety officer as referred to in section 7.6, the employer shall provide a hearing protector to every employee whose exposure is likely to exceed the maximum permitted levels prescribed in subsection 7.4(1).

It should be noted that the use of hearing protection is considered the last line of defence to protect the hearing of workers. If an employee's exposure to noise is in excess of 87 dBA ( Lex, 8 ), or exceeds the limits in the Schedule, and cannot be reduced by administrative or engineering controls or other physical means, in a reasonably practicable manner, the use of hearing protection is mandatory.

Paragraphs 7.7(2)(a) and (b) require the employer to consult with the work place committee or the health and safety representative to formulate a program to train employees in the fit, care and use of hearing protectors, and for the employer to implement a training program.

CSA Standard Z94.2-M1984, Hearing Protectors, as amended from time to time, which is referenced in the regulations, outlines the proper selection, fit, care and use of hearing protectors. If qualified personnel are available on site (e.g., occupational health nurse, hygienists, etc.), a hearing conservation program may be provided by them, or outside consultants may be hired, but the work place committee or the health and safety representative must be consulted in formulating the program. The approach is left up to the discretion of the employer, as long as each employee who is required to use hearing protection is adequately trained in the fit, care and use of hearing protection.

Subsection 7.7(3) requires that every person, other than an employee granted access to a work place where the exposure to sound is likely to exceed the prescribed limits shall use a hearing protector that meets the prescribed standards. It should be noted that the regulation does not require the employer to provide the hearing protection, only that the person granted access shall use one.

Warning Signs

Subsection 7.8(1) requires the employer to post and keep posted warning signs at a work place where employees may be exposed to A-weighted sound pressure levels greater than 87 dBA.

Warning signs should be visible and readily interpreted. Signs which are in the form of symbols are acceptable.

Subsection 7.8(2) prescribes that, for the purpose of subsection 7.8(1), the A-weighted sound pressure level shall be measured instantaneously using the slow response setting of a sound level meter, and these measurements shall be taken during normal working conditions.

Caroline Cyr
Director General / Directrice générale
Program Development and Guidance Directorate /
Direction du développement du programme et de l'orientation
HRSDC - Labour Program / RHDCC - Programme du travail


Flow Chart - Part VII of the COHSR (Levels of Sound)

Hazard Investigation (Section 7.3)

If an employee may be exposed to a noise level of 84 dBA or more for a period that is likely to endanger his/her hearing, the employer shall,

Appoint a qualified person to investigate and write a report;

Notify the OHS committee or representative of the investigation.

Note: the report must include observations and recommendations to ensure compliance with sections 7.4 to 7.8 of the COHSR and recommendations as for the use of hearing protectors.

Measurements must be made using a sound level meter on the slow response setting.

The report must be kept for 10 years.

If it is possible that Lex, 8 > 84 dBA , the employer shall permanently post the report and provide employees with written information on the hazards of exposure to high levels of noise.

Limits of Exposure (Section 7.4)

No employee shall be exposed during one 24 hours period, to noise that exceeds, the level and duration in the Schedule, or 87 dBA over 8 hours, (i.e. Lex, 8 87 dBA).

Reduction of Exposure (Section 7.5)

If the noise exposure exceeds, the level and duration in the Schedule, or 87 dBA over 8 hours ( Lex, 8 > 87 dBA ), the employer shall reduce the exposure as much as reasonably practicable by means other than providing hearing protectors.

Report to Regional Health and Safety Officer (RHSO) (Section 7.6)

If the exposure cannot be reduced below allowable limits without providing hearing protectors, the employer shall send a report explaining this to the regional health and safety officer, and provide a copy of the report to the health and safety committee or representative.

Hearing Protectors (Section 7.7)

If necessary, the employer shall provide employees with hearing protectors complying with CSA Z94.2, Hearing Protectors, and in consultation with the health and safety committee or representative establish a training program for the care and use of the protectors, and shall ensure that persons other than the employees who require hearing protectors, use protectors complying with CSA Z94.2.

Post Warning Signs (Section 7.8)

The employer shall permanently post warning signs when the noise level is > 87 dBA. Measurement must be taken using a sound level meter on the slow response setting.

The measurement and the calculation of the Lex, 8 must be made in accordance with Section 7.2 of the Regulation. To assure accuracy consult the official version of the Regulation.


[1] 74 dBA was chosen to reflect a requirement in the CSA standard referenced in 7.2(1) that the threshold level should be at least 10 dB below the level of 84 dBA prescribed in paragraph 7.3(4)(e). [back to text]

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