The ACGIH Heat Stress Guidelines and Why It Matters
Every year the summers are getting hotter, presenting serious threats to workers and individuals alike. While some professions are exposed to high temperatures all year round, the escalating temperatures make the need for organisations to understand the lurking dangers of heat stress more important than ever. There are many resources and tools available to provide recommendations to guide organisations and help safeguard workers, this is where the American Conference of Governmental Industrial Hygienists (ACGIH) comes in.
The ACGIH is a leading organisation in occupational safety and health that has developed a useful set of guidelines. These guidelines can be a valuable resource for organisations looking to protect their employees against heat stress. This blog delves into the guidelines, while highlighting how Bodytrak can help organisations comply and combat heat stress in the workplace.
What is the ACGIH?
The ACGIH also known as the American Conference of Governmental Industrial Hygienists is a leading non-profit organisation that consists of occupational safety and health professionals. With a mission to protect workers around the world, they use research and science supported by data to provide guidance on workplace hazards. This includes developing Threshold Limit Values (TLVs) that are recommended exposure limits for various workplace hazards, such as heat stress.
What is the difference between OSHA and the ACGIH?
The Occupational Safety and Health Administration (OSHA) is part of the United States Department of Labor. The US Congress created OSHA to set and enforce standards that maintains and protects the health and safety for workers while providing training, outreach, education and compliance assistance. According to the laws established under OSHA, employers have a responsibility to provide a safe and healthy workplace for their employees.
OSHA is a federal agency body that regulates workplace safety whereas the ACGIH is better recognised and respected as an organisation that studies occupational and environmental issues to provide recommendations. While OSHA and the ACGIH share a similar mission to protect workers, recommendations shared by the ACGIH cannot be legally enforced like the standards set out by OSHA.
Why are heat stress guidelines important?
Heat stress poses significant risks in the workplace. Both physical and mental capabilities can be compromised, increasing the risks of incidents, errors and decreasing productivity. Employees can encounter a number of heat-related illnesses ranging from heat exhaustion and cramps to heat stroke. These conditions can have debilitating long-term effects and can be life-threatening.
For heat-related incidents, prevention is often the best solution. By implementing heat stress guidelines in the workplace, organisations can proactively and significantly reduce the risk of heat-related illnesses to keep employees safe and create a healthy work environment.
Understanding the ACGIH heat stress guidelines
When the body maintains a consistent temperature, it is in thermal equilibrium. The guidelines developed by the ACGIH aim to help workers sustain this in order to reduce the risk of heat exhaustion or heat stroke. These guidelines are set around Threshold Limit Values (TLVs) and Action Limit (AL).
TLVs are based on the ability of healthy acclimatised workers to maintain thermal equilibrium while AL provides values for workers that are not acclimatised. These values aim to help limit heat stress exposure to those that may be sustained for hours. This leads to an evaluation process to determine whether a program to assess and mitigate the risks associated with heat stress is required. Examples of practices that can be used to mitigate the risk are adjusting work durations, work-rest schedules and hydration requirements.
There are four methods that can be implemented as part of the evaluation process stated in the ACGIH guidelines. Each method varies in complexity and levels of professional expertise required.
Method 1: Screening criteria based on Wet Bulb Globe Temperature
This method requires less effort than a complete evaluation highlighted in method 2.
This method uses the Wet Bulb Globe Temperature (WBGT) and estimated work rate. WBGT considers air temperature, humidity, radiant heat, and wind speed to provide an overview of the environment for predicting the heat stress that a worker experiences.
A table is then used to compare the WBGT to the TLV and AL. If it is less than the limit value for workers that are not acclimatised, then there is less risk of excessive heat exposure. If it is greater, then a plan is required to reduce the risk of a heat-related illness.
Method 2: TLV analysis
Compared to method 1 this is a more thorough approach. This requires the organisation to analyse the task to calculate the time-weight averages for WBGT and work rate. In order for this to be effective at least one cycle of work and rest is required when analysing the task. For instance, the recommended WBGT for continuous light work is 30°C / 86°F, while for heavy work with frequent breaks (75% rest), it jumps to 32.2°C / 90°F.
If exposure is less than the AL then no further action is required while preventative measures are recommended if exposure is greater than AL but lower than TLV. In the event that exposure is greater than TLV, action must be taken to lower the exposure to heat to reduce the TLV.
Method 3: Advanced heat stress evaluation
This refers to methods such as the predicted heat strain (PHS) model and the US Army Heat Stress Decision Aid (HSDA). The PHS model predicts core body temperature (CBT) and water loss over time, based on various environmental conditions such as air temperature, relative humidity, radiant temperature and air velocity as well as clothing and activity levels. This requires the data to be used to calculate heat strain. Similarly, the HSDA also predicts CBT when individuals are wearing chemical protective clothing, combat uniforms, and cold weather clothing.
Method 4: Heat strain and physiological monitoring
As highlighted in the ACGIH guidelines this is an alternative method to WBGT. WBGT monitors the ambient temperature in the environment. While it can be a useful method for measuring environmental temperatures, the ACGIH recognises the individual variations in heat tolerance.
When monitoring individual physiological responses to increasing temperatures this takes into consideration other factors that can influence a worker’s susceptibility to heat stress. This is something that is not accounted for when using WBGT, as it measures the environment not the individual. Many factors influence a worker’s response to varying temperatures including, age, weight, pre-existing medical conditions, medication and lack of acclimatisation. To better understand the risks that impact the rate of heat related illnesses please read ‘Who is most at risk when it comes to heat-related illnesses?’. The ACGIH guidelines acknowledge these factors and others such as clothing and personal protective equipment (PPE) that can influence heat stress. Organisations must recognise this when developing internal policies and procedures.
Monitoring core body temperature
To better understand an individual’s physiological responses in hot conditions, the ACGIH recommends monitoring core body temperature alongside WBGT. While the guidelines highlight the gastro-intestinal (GI) pills, tympanic temperature and skin temperature as approaches to monitor core body temperature. Some of these may be impractical, inaccurate or too costly in industrial settings. For instance, consuming food or drinks after swallowing a GI pill can implicate the temperature reading and the external monitor to obtain the reading also needs to be within a close range to detect the data. Similarly, measuring skin temperature does not provide an accurate CBT reading as it can be influenced by the temperature of the air, or heat trapped under existing PPE and movement.
With the evolution of technology, there are now new methods that can monitor CBT accurately in real-time suitable for use in industrial settings and avoiding any hindrance of workers performing their usual activity. Bodytrak is an in-ear solution that fits comfortably in the ear, taking an internal reading of the body’s temperature. Due to its proximity to the hypothalamus, the body’s temperature control organ, the ear is an excellent place to measure core body temperature (CBT) and heart rate.
Nestled securely in the ear, Bodytrak is unaffected by abrupt changes in environmental conditions and movement, delivering consistent and accurate data unique to the working wearing the device. The CBT data from Bodytrak is validated against the gastro-intestinal pill, showing a mean absolute error of 0.18°C. This ensures accurate readings of CBT are obtained and any early signs of heat stress can be reliably detected.
The ACGIH have determined that CBT should not increase by more than 1°C before work has begun if the CBT is less than 37.5°C. The ACGIH guidelines recommend organisations should set a limit at 38.5°C. This value is considered important because a CBT higher than 39°C often indicates a loss of thermal regulatory control or increased risk of heat stress. Setting a lower threshold allows a margin of error in measurement and provides time for intervention. The Bodytrak solution reduces the complexity by allowing organisations to preset thresholds on the device so that when a user’s CBT reaches this threshold they can receive an audio alert. At the same time, a supervisor would also receive the alert in real-time via the Dashboard, text, email and WhatsApp to ensure support and early intervention is provided.
Benefits of complying with ACGIH heat stress guidelines
By keeping employees safe and implementing the ACGIH heat stress guidelines both organisations and workers can benefit.
Reduced risk of heat-related illnesses
Proper heat stress management protects workers from debilitating and potentially life-threatening illnesses.
Improved productivity
Heat stress can significantly decrease worker performance and can also result in employee absenteeism. Maintaining a cool and comfortable working environment leads to better focus and increased productivity while mitigating the risks of incidents.
Lower costs
Heat-related illnesses can lead to expensive medical and legal costs. Implementing heat stress guidelines can prevent and minimise the need for such expenses to the employer and employee as a result of an incident.
Enhanced employee morale
A safe and healthy work environment fosters better employee morale and reduces employee turnover.
How Bodytrak helps organisations comply with ACGIH guidelines
When trying to digest any new set of guidelines it can seem challenging however, a solution like Bodytrak is designed to make it easier while still remaining effective in the workplace. The comprehensive smart safety solution from Bodytrak uses real-time, actionable data to better manage heat stress in different workplaces around the world. When looking at the ACGIH guidelines Bodytrak is an effective solution that can help organisations comply with method 4 – heat strain and physiological monitoring.
Real-time monitoring
Sensors in the in-ear solution monitor a number of physiological responses including CBT, heart rate, heart rate variability and physiological strain to provide instant insights into each individual’s responses to activities in the workplace.
Personalised alerts and notifications
The Incident Management Platform allows the organisations health and safety professionals to set up alerts based on the ACGIH thresholds that includes the CBT limits. Workers using the device will receive audio alerts when they approach levels that can put them at risk while supervisors also receive notifications, ensuring preventative action is taken.
Insightful reporting
The data captured can be utilised to make well-informed decisions based on scientific data to design, implement and evaluate work-rest schedules, work intensity and individual processes and needs to ensure worker safety and optimal performance.
