Air quality is a critical aspect of indoor environments, significantly impacting occupant health, comfort, and overall well-being. Occupational exposure limits, such as the American Conference of Governmental Industrial Hygienists (ACGIH^®) threshold limit values (TLVs^®), serve as important benchmarks, setting thresholds for acceptable levels of airborne contaminants to protect employees from adverse health effects. At the same time, comfort considerations such as temperature, relative humidity, and indoor air quality (IAQ) pollutants help create environments that contribute to productivity and well-being. To have good air quality and employee satisfaction, there must be a comprehensive understanding of all these factors, as well as an effective ventilation system. Established standards and guidelines must be followed.

Note: The underground mining regulations and Part 12 of the Occupational General Safety Regulations provide further requirements associated with air quality and ventilation specific to those high-risk hazards.

An employer must: [N.S. Reg. 44/99, s. 15]

• Make sure there is enough fresh air coming into the workplace and that the air is clean.
• Manage exposures to any harmful gases, vapours, dust, or other impurities (i.e., air contaminants) that could make people sick.
• Use mechanical ventilation to eliminate or reduce any air contaminants produced in the workplace to stop people from breathing them in. These systems should also get rid of the air contaminants effectively and make sure they do not re-enter the workplace.
• Make sure that all ventilation systems used to control the spread of air contaminants are set up, used, and maintained properly by competent persons, such as engineers and occupational hygienists.

Regarding temperature, the employer must monitor the temperature in work environments and compare it to the TLV^® for heat stress and cold stress.

• If the temperature exceeds the TLV^® for heat stress, employers need to take action to reduce exposure. Measures may include providing cooling stations, scheduling frequent breaks in cooler areas, ensuring adequate hydration, and using engineering controls like ventilation and air conditioning to lower ambient temperatures.
• If the cold temperature falls below the TLV^® for cold stress, employers need to take action to minimize cold exposure. Measures may include providing warm shelters, scheduling frequent breaks in warmer areas, ensuring appropriate clothing and insulation, and using heating systems to raise ambient temperatures.

By following the ACGIH^® TLV^® for heat stress, employers can help protect people from the risks associated with excessive heat exposure, including heat exhaustion, heat stroke, and other heat-related illnesses. Similarly, the ACGIH^® TLVs^® for cold stress will help protect employees from the most severe effects, such as hypothermia and frostbite. Regarding air contaminants, the employer must make sure that:

• Any air contaminant is kept at a level that does not pose a hazard to an employee and, where a TLV^® exists, that the exposure of an employee at no time exceeds the TLV^® without adequate control measures put into place.
• If you or your employee has reason to believe that the level of concentration of an air contaminant may be approaching the TLV^®, the air is tested to determine the contaminant’s concentration level.
• Engineering controls are designed, installed, and maintained according to good engineering practices.
• When ventilation is used as an engineering control, the air contaminant is controlled at the source by an effective local exhaust ventilation system.
• If local exhaust ventilation is not possible, use general ventilation or a combination of general and local exhaust ventilation.
• A local exhaust ventilation system is designed so that under normal work conditions, the employee’s breathing zone is not in between the source of contamination and the exhaust uptake.
• The ventilation system is not obstructed or blocked by any material or equipment that is placed in front of the ventilation openings.
• The local exhaust ventilation system stays working until the operation or work process is completed and the air contaminants generated are at a level that is not a hazard.
• The local exhaust ventilation system is regularly inspected and monitored to make sure it stays effective.
• An adequate supply of makeup air is provided to maintain the effectiveness of the system and prevent air contaminants from being drawn into the work area from another area; the make-up air must not be a hazard to the health of employees.
• A respirator is provided to an employee, and the employee wears the respirator when engineering controls are not practical or when the engineering controls are being installed.
• When it can be reasonably expected to be a danger, exhaust from any internal combustion engine operated indoors is vented to the outdoors.
• When internal combustion engines are operated indoors (such as those on powered mobile equipment or industrial lift trucks), assess the work area for potential exposure to exhaust contaminants, and reduce the concentration of contaminants by adequately servicing and maintaining the engine.
• When regularly operated indoors without adequate ventilation, any powered mobile equipment, industrial lift truck, or other equipment powered by an internal combustion engine must be equipped with an alarm to warn workplace parties that carbon monoxide poses an imminent risk.
• When employee exposure to an air contaminant occurs in a timeframe other than an eight-hour work day within a 40-hour work week, that the Brief and Scala model (latest version of the ACGIH^® publication Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices) is used to adjust the TLV^® and that employee exposure to the air contaminant does not exceed the adjusted TLV^®.
  • Adequate respiratory protective equipment is provided to each employee where:
• The level of concentration of an air contaminant exceeds the TLV under normal working conditions.
• There is the possibility of accidental exposure to concentration exceeding the TLV.
• The oxygen content is less than or may be less than 19.5%.
• When work is completed in an area where dust may create a hazard to employees, controls are in place to protect employees.
• Where a process generates a combustible dust hazard, such as wood particulate, organic matter, or metals, the ventilation systems are designed, maintained, and used following appropriate safety standards and regulations to minimize the risk of fire or explosion.

Regarding mechanical ventilation systems, the employer must make sure that:

• Electrical components of an exhaust ventilation system meet the requirements of the latest version of the CSA Standard, C22.1 “Canadian Electrical Code, Part 1”. Surface mines must follow CSA M421 “Use of Electricity in Mines” for all electrical installations. [N.S. Reg. 44/99, s. 120]
• All ventilation systems are set up, used, and maintained properly by competent persons
• Adequate industry standards, such as ACGIH® Industrial Ventilation Manuals are considered for the design, use, and maintenance.

Threshold limit values

Employers must adhere to the threshold limit values (TLVs^®) and biological exposure indices (BEIs^®) for gases, vapours, mists, fumes, smoke, dust, chemical substances, and physical agents, ensuring compliance with these standards to protect employees’ health. [N.S. Reg. 52/2013, s. 2.3]

What are TLVs?

Threshold limit values (TLVs^®) refer to established standards which represent the concentrations of chemical substances and conditions deemed safe for nearly all healthy employees to be exposed to repeatedly over a working lifetime without adverse health effects. Similarly for physical agents, TLVs^® indicate exposure levels and conditions considered safe for nearly all healthy employees to endure repeatedly without negative health consequences.

Fungi (mould)

Employers must implement measures to prevent mould growth and promptly address any mould-related concerns to protect the health and safety of their employees. Respiratory issues are a major occupational health risk linked to mould exposure. Inhalation of mould spores and their byproducts can lead to allergic reactions, asthma exacerbation, respiratory infections, and other respiratory problems. Prolonged exposure to mould in the workplace can also trigger or worsen existing respiratory conditions, affecting the overall health and well-being of employees. Additionally, mould exposure may cause skin and eye irritation, headaches, fatigue, and other symptoms, impacting employee’s productivity and quality of life.

Employers must follow industry standards, such as the Canadian Construction Association’s Mould Guidelines for the Canadian Construction Industry for mould remediation (see Resources for link). This duty involves implementing comprehensive strategies outlined in the guidelines to identify, assess, and safely remove mould from indoor workplaces. Additionally, employers must provide appropriate training, personal protective equipment, and resources to employees involved in mould remediation activities to ensure their health and safety. By following these guidelines diligently, employers can effectively eliminate or reduce the risks associated with mould exposure and create safer working environments for their employees.

Indoor Air Quality (IAQ)

TLVs^® specifically target airborne contaminants in occupational settings to protect employees, while general IAQ considerations encompass a broader range of factors to ensure overall indoor comfort and health for occupants in various indoor environments. Although not a requirement in regulations, employers should consider addressing these comfort parameters to help create indoor environments that support occupant well-being, productivity, and satisfaction, such as:

• Temperature: Maintaining a comfortable temperature range, typically between 20 to 26 degrees Celsius (68 to 78 degrees Fahrenheit), ensures occupants feel neither too hot nor too cold.
• Relative Humidity: Controlling relative humidity levels between 30% to 60% helps prevent issues such as mould growth, condensation, and discomfort caused by excessively dry or humid air.
• Indoor Air Quality Pollutants: Ensuring low levels of indoor air pollutants such as volatile organic compounds, particulate matter, carbon dioxide, and other contaminants to promote a healthy and pleasant indoor environment.
• Ventilation: Providing adequate ventilation rates to supply fresh outdoor air and remove indoor pollutants, ensuring a constant supply of oxygen and preventing the buildup of stale air.
• Air Movement: Proper air circulation and distribution throughout the space to avoid stagnant air pockets and maintain consistent comfort levels across different areas.

ANSI/ASHRAE Standard 62.1-2022 specifies requirements for ventilation and acceptable indoor air quality. It includes standards for temperature, relative humidity, particulate matter levels, and other parameters to ensure a healthy indoor environment. While the employer is ultimately responsible for all the provisions mentioned above, the supervisor has a vital role to play in the safety of their teams. As a supervisor, you must:

• Acquaint your employees with the hazards and control measures associated with their work.
• Provide the information and instruction necessary to ensure their health and safety.
• Enforce company safety rules, programs, codes of practice and procedures, including ensuring employees comply with the requirements below.

An employee must:

• Follow any instruction, education or training provided by your employer about air quality and use any equipment that is required (including personal protective equipment).
• Be aware of changing conditions.
• Report any hazards to your employer or supervisor.

Service Providers

Service providers must take precautions to ensure the safety of individuals in workplaces and the accuracy of the information they provide. This duty includes alerting to any harm that may be the result of their activities and ensuring that any information they offer is accurate and comprehensive enough for recipients to make informed decisions. Compliance with these precautions is essential to safeguard the health and well-being of all workplace parties and the public, and to make sure workplaces meet standards for air quality, ventilation, and other comfort parameters outlined in relevant regulations and guidelines.