Introduction
Heat is not just an outdoor concern – high temperatures and humidity inside industrial facilities can create dangerous conditions for workers. Foundry floors, manufacturing plants, and warehouses can become heat traps, especially in summer. Understanding the heat index is crucial to keeping workers safe and staying compliant with emerging safety regulations.
In this article, we break down what the heat index is, why it matters in industrial settings, how to measure it (even indoors with hot equipment), and what solutions (like sensor-based monitors) can help. We’ll also touch on new OSHA rules that make heat hazard management a must for employers.
What is the Heat Index?
The heat index (also known as the apparent temperature) is a measure of what the air feels like to the human body when you combine the air temperature with relative humidity. In simple terms, it’s how hot it actually feels rather than what the thermometer reads. For example, you might see a weather report say “85°F but feels like 95°F” – that “feels like” number is the heat index.
Why Humidity Matters
Our bodies cool off by sweating and evaporation. When sweat evaporates from your skin, it carries away heat and lowers your body temperature. However, if the air is already filled with moisture (high humidity), sweat evaporates more slowly. That means on a humid day, your body can't cool itself as effectively, and it feels hotter than the actual air temperature. On the other hand, in dry air, sweat evaporates quickly and you feel a bit cooler than the thermometer reading.
The saying goes, “It’s not just the heat, it’s the humidity” – and the heat index captures both.
Heat Index Formula
The heat index is calculated from temperature and relative humidity. Meteorologists have derived an equation (from experimental data) to approximate the heat index:
Heat Index (°F) = -42.379 + 2.04901523T + 10.14333127R - 0.22475541TR - 0.00683783T² - 0.05481717R² + 0.00122874T²R + 0.00085282TR² - 0.00000199T²R²
This formula looks complicated because it was obtained by regression analysis (with an accuracy of about ±1.3°F). The good news: you don’t need to crunch this formula by hand. Most people use heat index charts or calculators to get the result quickly. Here's a chart that's provided by the National Weather Service.
Find the original chart at the National Weather Service website.
For instance, if the air temperature is 98°F and the relative humidity is 55%, the heat index will be about 117°F, meaning it feels like 117°F to a person. Conversely, at low humidity, the heat index can be lower than the actual temperature (dry air makes it feel cooler).
Importance of Measuring Heat Index in Industrial Workplaces
Measuring the heat index is crucial for worker safety in industrial settings. A plain temperature reading doesn’t tell the full story of heat stress risk. A factory floor at 90°F with high humidity can be far more dangerous than a climate-controlled space at the same temperature. Monitoring the heat index gives facility managers a clearer picture of conditions and helps prevent heat-related illnesses and accidents.
Heat Stress and Health Risks
High heat index levels increase the risk of heat exhaustion and heat stroke:
-
Heat Exhaustion: Symptoms include dizziness, headache, nausea, rapid pulse, and heavy sweating. If untreated, it can lead to heat stroke.
-
Heat Stroke: A life-threatening condition where the body fails to regulate temperature. Symptoms include confusion, loss of consciousness, and convulsions. Heat stroke can be fatal.
Heat stress also increases fatigue, which can lead to workplace accidents, such as falls or mishandling machinery.
Indoor Heat Hazards
Indoor workplaces can become dangerously hot, especially in foundries, warehouses, and glass manufacturing plants. Heat-generating equipment, poor ventilation, and protective gear contribute to worker heat stress. Monitoring the heat index in such environments is essential to identifying hazardous conditions and taking preventive action.
OSHA’s Proposed Heat Hazard Regulations
The U.S. Occupational Safety and Health Administration (OSHA) has proposed a new standard called “Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings.” This rule (currently in the proposal stage) would apply to virtually all employers with hot work environments, both outdoors and indoors.
What the Rule Requires
OSHA’s proposed standard is programmatic, meaning employers must develop a heat hazard prevention plan. This includes measures like monitoring conditions, training workers on heat safety, providing water and rest breaks, and emergency planning.
A key part of the proposed OSHA rule is monitoring environmental conditions. OSHA explicitly notes that assessing heat hazards should include measuring temperature and heat index. Measuring the heat index isn’t just for health—it’s increasingly a compliance issue. Employers need to document and respond to heat index levels to meet the forthcoming OSHA requirements.
How to Measure Heat Index in the Workplace
Measuring the temperature outdoors is pretty straightforward and it can be found on most weather apps, indoor is more tricky. Measuring the heat index involves measuring two things: temperature and humidity. Here are a few methods and considerations:
-
Thermometer + Hygrometer: Technically you can use a thermometer (for air temperature) and a hygrometer (for relative humidity) and plug those readings into a calculator. This approach probably isn't cost-effective or practical (unless you're already measuring temperature and humidity).
-
Digital Heat Index Monitors: Portable meters automatically compute the heat index and display it in real-time. Often you'll see these meters referred to as WBGT (Wet Bulb Globe Temperature) meters.
-
Continuous Monitoring Sensors: Electronic sensors track temperature and humidity in real-time, logging data and sending alerts when conditions become unsafe. These devices are usually fixed and can actually be more affordable than WBGT meters. We'll cover one of our favorite remote monitoring solutions, the GS1 later in the article.
Challenges in Indoor Measurements Measuring heat index indoors isn’t always straightforward. The standard heat index assumes shade with no direct radiant heat. However, many industrial settings have radiant heat sources like molten metal or ovens, which can make it feel even hotter than what the air temperature alone would indicate.
IOthrifty Product Solutions for Managing Heat Index
GS1 Industrial Grade WiFi/4G Data Logger
Using a continuous monitoring system can be a game-changer. One example solution is an industrial-grade WiFi/4G temperature & humidity data logger. This type of device constantly measures ambient temperature and humidity, sending real-time data to a cloud platform.
Key Features:
-
Real-time data logging and remote alerts
-
Battery-powered with external power options
-
Easy to set up
-
Affordable
By actively monitoring conditions and keeping records, employers can ensure worker safety and compliance with OSHA regulations.
Conclusion
Heat index awareness is a vital part of modern industrial safety. By understanding how temperature and humidity combine to stress workers, facility managers can make better decisions to protect their teams. Measuring the heat index in the workplace – and knowing when it’s entering the danger zone – allows for proactive safety measures.
With OSHA moving toward stricter heat illness prevention rules, proactive monitoring is becoming an expected standard. Fortunately, tools like heat index charts, guidelines, and affordable sensors make it easier than ever to stay informed. By investing in heat index education and monitoring, industrial professionals can ensure a safer, healthier workplace – even when the heat is on. Stay safe, stay cool!
If you need any assistance finding the right solution for your heat index monitoring needs, head over to IOThrifty.com or contact us at service@iothrifty.com.