--- title: "Heat Stress & WBGT Monitoring for Outdoor Work | Aethair" description: "Heat-stress monitoring for outdoor work crews, athletics, military training, and public events: wet bulb globe temperature (WBGT) against the ACGIH…" url: https://aethair.io/solutions/heat-stress/ --- Aethair solutions # Heat Stress & Outdoor Work WBGT for worksites, athletics, and events Heat-stress monitoring for outdoor work crews, athletics, military training, and public events: wet bulb globe temperature (WBGT) against the ACGIH heat-stress TLV, plus supporting air temperature, humidity, wet bulb, and heat index. [Schedule a call](https://calendly.com/d/ctdd-mkr-v9v/aethair-demo-website) [Build a Configuration](https://aethair.io/build/?params=wbgt\&solution=heat-stress) At a glance 1 core parameter [WBGT (Heat Stress)](https://aethair.io/parameters/wbgt/) 2 devices cover it - **Thiamis** TSI Heat Stress & Comfort 1 standard sets limits - [ACGIH ACGIH Heat-Stress TLV (WBGT)](https://aethair.io/standards/acgih_wbgt/) Why it matters ## Why Outdoor Work Monitors Heat Stress When people work or exert themselves in the heat, their bodies can gain heat faster than they can shed it, leading to heat exhaustion, heat stroke, and, in the worst cases, death. The risk depends not on air temperature alone but on the combination of heat, humidity, radiant load from the sun, and air movement, together with the intensity of the work and what the person is wearing. Employers, sports bodies, the military, and event organizers all have a duty to manage that risk, and doing so means measuring the actual thermal environment rather than guessing from a thermometer. Heat-stress monitoring provides the objective basis for work-rest cycles, hydration schedules, activity limits, and the decision to stop. As hot spells become more frequent and severe, this shift from ad hoc judgment to measured heat-stress assessment is increasingly built into occupational and sports safety practice. What to measure ## What to Measure and the Limits That Apply The core panel covers the main program. Other parameters are added for a specific site or requirement. Every limit below is the published value from the standard that sets it. The central metric is **wet-bulb globe temperature (WBGT)**, the index that combines air temperature, humidity, radiant heat, and air movement into a single figure and is assessed against the **ACGIH heat-stress TLV** and similar occupational guidance to set safe work-rest limits. Behind it sit the parameters WBGT is built from: **air (dry-bulb) temperature**, **humidity**, **wet-bulb temperature** (reflecting evaporative cooling), and the radiant load from a black-globe measurement. **Heat index** offers a familiar shade-based figure combining temperature and humidity for general awareness. Measuring these together captures why a moderate air temperature can still be dangerous in strong sun, high humidity, or still air. WBGT (Heat Stress) Meteorology [**31 °C** *TLV, acclimatized, light work (75–100% work)* · ACGIH WBGT](https://aethair.io/standards/acgih_wbgt/) [**28 °C** *TLV, acclimatized, moderate work (75–100% work)* · ACGIH WBGT](https://aethair.io/standards/acgih_wbgt/) [**27.5 °C** *TLV, acclimatized, heavy work (50–75% work)* · ACGIH WBGT](https://aethair.io/standards/acgih_wbgt/ "no TLV is set for heavy work at 75–100% work time, because that work is not recommended") [**25 °C** *Action limit, unacclimatized, moderate work (75–100% work)* · ACGIH WBGT](https://aethair.io/standards/acgih_wbgt/ "ACGIH screening values; adjust for work/rest allocation and clothing") Wet bulb globe temperature is the standard index for managing heat stress in outdoor work, athletics, military training, and events, because it combines humidity, radiant heat, air movement, and air temperature into the single number that heat-safety programs are written around. Continuous WBGT monitoring at the activity location drives the work-rest, hydration, and rescheduling decisions that prevent heat illness as conditions climb. - **ACGIH WBGT** 27.5 °C: no TLV is set for heavy work at 75–100% work time, because that work is not recommended - **ACGIH WBGT** 25 °C: ACGIH screening values; adjust for work/rest allocation and clothing [WBGT (Heat Stress): sensors, units, and every standard](https://aethair.io/parameters/wbgt/) Air Temperature Often added · Meteorology Ambient air (dry-bulb) temperature. [Air Temperature: sensors, units, and every standard](https://aethair.io/parameters/temperature/) Relative Humidity Often added · Meteorology Relative humidity of air. [Relative Humidity: sensors, units, and every standard](https://aethair.io/parameters/humidity/) Wet Bulb Temperature Often added · Meteorology Wet-bulb temperature: an input for evaporative cooling and heat-stress calculations. [Wet Bulb Temperature: sensors, units, and every standard](https://aethair.io/parameters/wet_bulb/) Heat Index Often added · Meteorology Heat index / apparent temperature combining heat and humidity. [Heat Index: sensors, units, and every standard](https://aethair.io/parameters/heat_index/) Solar / Global Radiation Often added · Radiation & Light Global (solar) radiation / irradiance. [Solar / Global Radiation: sensors, units, and every standard](https://aethair.io/parameters/solar_radiation/) **Methods and guidance:** [ISO 7243: heat stress assessment with the WBGT index](https://aethair.io/standards/iso_7243/) The setup ## How a Monitoring Setup Works Heat-stress monitoring uses a Thiamis gateway connected to a WBGT sensor set (the dry-bulb, natural wet-bulb, and black-globe measurements that combine into the index), sited where the work or activity actually happens, in the sun and conditions the people experience. The logger records continuously and computes WBGT and heat index, driving alerts as the index approaches the threshold for the current workload so that work-rest cycles or a stoppage can be applied in time. Because radiant load is part of the index, a shaded reading is not enough: the black globe must sit in the same exposure as the workers. One station represents a work area with a consistent environment. The recommended configuration below builds a WBGT heat-stress station. Use the configurator to add parameters or extra locations for your site. [Customize this configuration](https://aethair.io/build/?params=wbgt\&solution=heat-stress) Which monitor ## The Instruments in This Configuration A [Thiamis](https://aethair.io/products/thiamis/) gateway logs these instruments continuously and sends their readings to Environet over 4G LTE (cellular data included) or the site's Wi-Fi. There they get the same alerts, reports, dashboards, and API as any Aethair monitor, in one account with every other device on the site, instead of a separate vendor app for each instrument. Thiamis runs on mains power, a solar panel, or an external battery. ### [TSI Heat Stress & Comfort](https://aethair.io/sensors/tsi-heat-stress-comfort/) TSI Quest QUESTemp° area heat-stress (WBGT) monitors. [How Thiamis connects them](https://aethair.io/products/thiamis/) What you get ## Readings, Alerts, and the Report That Proves It Every reading goes to the Aethair platform. Here is what a monitoring program gets from it. ### [Live data and alerts](https://aethair.io/platform/environet/) Every reading in Environet as it happens, with alerts by email, SMS, or webhook at the thresholds you set. ### [Compliance reports](https://aethair.io/platform/reports/) Scheduled or on-demand reports against the standards above or your own limits, as PDF or a secure link. ### [Dashboards and AI analysis](https://aethair.io/platform/dashboards/) Live displays for a site or the public, and Noesis answering questions about the data in plain language. ### [Your data, through the API](https://docs.environet.io/) Live and historical readings as JSON or CSV through the Environet API (OpenAPI 3.2), for a building management system, an ERP, or your own applications. The data is yours. [See a sample report](https://aethair.io/docs/aethair-hq-first-floor-report-example.pdf) Article Library ## Reading for Heat Stress & Outdoor Work ### [OSHA Air Quality Standards 2026: PELs & 29 CFR 1910.1000](https://aethair.io/resources/osha-air-quality-standards-compliance/) OSHA air quality standards for indoor and outdoor work: permissible exposure limits, Table Z-1, 29 CFR 1910.1000, and the heat and wildfire smoke triggers. [All articles](https://aethair.io/resources/) Related solutions ## Related Solutions ### [Weather Stations & Meteorology](https://aethair.io/solutions/weather/) Professional multi-parameter weather monitoring ### [Occupational Safety & Industrial Hygiene](https://aethair.io/solutions/occupational-safety/) Worker exposure, confined space, and heat stress [All solutions](https://aethair.io/solutions/) Questions ## Heat Stress & Outdoor Work FAQ What is WBGT and why is it used for heat stress? Wet-bulb globe temperature is an index that combines air temperature, humidity, radiant heat, and air movement into a single figure representing the real thermal load on the body. It is used for heat-stress assessment because those factors together, not air temperature alone, determine the risk. That is why it underpins the ACGIH heat-stress TLV and similar guidance. How does WBGT differ from the heat index? The heat index combines temperature and humidity for a shade-based measure of how hot it feels, whereas WBGT also accounts for radiant heat from the sun and air movement, and is measured in the actual exposure. That makes WBGT the more complete index for outdoor and occupational heat-stress decisions, with the heat index useful for general awareness. Why must the sensor sit in the sun rather than the shade? Radiant heat from the sun is a major part of the load on a working body and is captured by the black-globe measurement within WBGT. A reading taken in the shade misses that radiant component and understates the risk, so the sensor must be exposed to the same sun and conditions the workers face. How do the WBGT limits change with the work pattern? The ACGIH screening values fall as the share of each hour spent working rises and as the work gets heavier. For acclimatized workers doing moderate work the TLV is 28 °C at 75–100 % work, 29 °C at 50–75 %, 30 °C at 25–50 %, and 31.5 °C at 0–25 %; unacclimatized workers use the lower Action Limit (25 °C for moderate work at 75–100 %). Clothing heavier than a light work uniform needs an adjustment added to the measured WBGT. What is the best setup for heat-stress monitoring? A Thiamis gateway with a WBGT sensor set (dry-bulb, wet-bulb, and black-globe) sited in the workers' actual exposure, computing WBGT and heat index continuously with alerts tied to the workload. Use the configurator to build the station and add locations for each work area.