Now that we are coming out of the winter months we can expect warmer temperatures and longer days. As nice as this is, we need to be mindful of some of the hazards associated with the extra sun and heat exposure.

Heat Stress & Strain

This can be a serious danger to people working outdoors who are exposed to direct sun and also to those working in indoor environments that are impacted by warmer ambient temperatures and radiant heat from processes in the work area.

Some signs of heat strain include:

  • Body core temperature of 38.5 o C (normal body temperature is 37 oC)
  • Symptoms such as sudden and severe fatigue, nausea, dizziness, light-headedness


Outdoor workers can mitigate the effects of sun exposure by following simple steps such as:

  • Staying hydrated with water and electrolyte fluids
  • Wearing appropriate clothing to promote heat removal from the body by evaporation (sweating)
  • Applying sunscreen with an appropriate SPF number
  • Taking breaks and using shade when necessary
  • Job acclimatization where by a worker is eased into a task to minimize heat strain

Indoor work environments that contain radiant heat should ensure:

  • Proper shielding exists
  • Workers are wearing appropriate clothing
  • Ventilation maintains an appropriate ambient temperature
  • Appropriate air velocity is maintained (fan usage)

Legal Requirements
Ministry of Labour (MOL) Requirements

There is no specific regulation that enforces heat stress and strain, however the General Duty clause in the Occupational Health and Safety Act 25(2)(h) states that employers must take every precaution reasonable in the circumstances for the protection of the worker. ? There are guidelines that can be found on the MOL website or the ACGIH website

It is recommended that employers follow ACGIH guidelines and prevent unacclimatized workers core body temperature from rising above 38 ?C. ? It is recommended that hot environment policies and procedures are developed to prevent heat stress related illness in the workplace.

Worker Exposure Monitoring

Airzone can provide assistance to employers in assessing worker exposure to environments that could cause heat stress and heat stress related illness. ? We have equipment available to monitor ambient temperatures to determine if heat stress situations exist and additional equipment to monitor a person s body temperature.

OHS Updates

Reminder: ? Ontario has updated O.Reg. 833 as of July 1st 2010. ? Exposure limits for biological and chemical agents can be found in Table 1 of the regulation. ? Should the agent not exist in Table 1, then the ACGIH Table applies and must be referenced. ? Exposure cannot exceed the TWA, STEL, or Ceiling values.

Individual Designated Substance Regulations were repealed and grouped under O.Reg. 490/09.

If you would like further information on heat stress or if we can help you with any questions or assessments relating to occupational hygiene, please contact us and we will be more than happy to assist you with your needs.

Ryan Dignard: (905)-890-6957 ? Ext. 103 or 416-892-6924

Charles Geen: (905) -890-6957 ? Ext. 104