Aethair solutions
Occupational Safety & Industrial Hygiene
Worker exposure, confined space, and heat stress
Why it matters
Why Industrial Workplaces Monitor Exposure
Industrial workplaces can expose people to hazards that injure or kill: toxic gases, oxygen-deficient or explosive air, harmful dust, damaging noise, and dangerous heat. Occupational health and safety law places a duty on employers to assess these exposures and keep them below defined limits, and to prove it through monitoring and records. The frameworks are specific and enforceable: OSHA permissible exposure limits and ACGIH threshold limit values for gases and dust, confined-space atmospheric rules, occupational noise exposure limits, and heat-stress thresholds. Failing to monitor is both a legal liability and, more importantly, a direct risk to workers' lives and long-term health.
Industrial hygiene monitoring turns these duties into managed risk: it identifies which tasks and areas drive exposure, verifies that controls work, and documents compliance.
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 hazards cluster into families. Toxic and asphyxiant gases (carbon monoxide, hydrogen sulfide, oxygen level, and combustible gas, or LEL) are the core of confined-space and process safety, extended with NO₂, NO, SO₂, ammonia, chlorine, hydrogen chloride, hydrogen fluoride, and mercury vapor where specific processes demand. Respirable dust and crystalline silica cover particulate exposure. Noise (time-weighted average and peak) protects hearing, and WBGT heat stress protects against heat illness in hot work. Which of these apply depends on the process; an industrial hygiene assessment identifies the relevant subset for each role and area.
Carbon monoxide is a core industrial-hygiene and confined-space hazard because it is colorless, odorless, and binds to hemoglobin far more readily than oxygen, incapacitating workers before they sense it. Continuous CO monitoring in the breathing zone, with alarms set to the entry and exposure limits, is a primary safeguard wherever combustion, engines, or process sources can release it.
- OSHA confined space 35 ppm: not set by 1910.146, which defers to the OSHA PEL (50 ppm, 8-hour TWA); 35 ppm is the NIOSH REL and a common gas-detector alarm setpoint
Hydrogen sulfide is among the most dangerous gases in industrial and confined-space work: toxic at low concentrations, and treacherous because it deadens the sense of smell so workers cannot rely on its characteristic odor as a warning. Continuous H₂S monitoring in the breathing zone is essential in oil and gas, wastewater, and any operation where organic matter decays or sour gas is present.
- NIOSH REL 10 ppm: 10-minute
- OSHA confined space 10 ppm: not set by 1910.146, which defers to the OSHA limit (a 20 ppm ceiling); 10 ppm is a common gas-detector alarm setpoint
Oxygen monitoring is the first test of any confined-space entry, because both oxygen deficiency (which suffocates without warning) and oxygen enrichment (which sharply raises fire risk) are lethal hazards in enclosed spaces. A multi-gas monitor watches oxygen continuously during occupancy, since ventilation, work activity, and displaced or consumed gas can change the level after entry begins.
Oxygen (O₂): sensors, units, and every standardCombustible-gas monitoring, expressed as a percentage of the lower explosive limit (LEL), guards against the flammable atmospheres that cause catastrophic industrial explosions. It is a standard element of confined-space entry and process safety, tested after oxygen and alarming well below the explosive threshold so that work stops and the space is ventilated before any risk of ignition.
Combustible (LEL): sensors, units, and every standardSulfur dioxide: a criteria pollutant from fossil-fuel combustion that irritates the respiratory system.
Sulfur Dioxide (SO₂): sensors, units, and every standardNitrogen dioxide: a criteria pollutant, respiratory irritant, and marker of traffic combustion.
Nitrogen Dioxide (NO₂): sensors, units, and every standardAmmonia; a toxic, pungent gas from agriculture, refrigeration, and wastewater.
Ammonia (NH₃): sensors, units, and every standardChlorine gas; a toxic oxidizing irritant.
- NIOSH REL 0.5 ppm: 15-minute
Total volatile organic compounds: a broadband, PID-based indicator of solvent and fuel vapors.
VOC (Total): sensors, units, and every standardMercury vapor: a neurotoxic heavy-metal vapor.
- Cal/OSHA PEL 0.025 mg/m³: metallic and inorganic mercury
- Cal/OSHA PEL 0.1 mg/m³: metallic and inorganic mercury
- NIOSH REL 0.05 mg/m³: mercury vapor; skin
Wet-Bulb Globe Temperature (WBGT): the standard composite index for occupational heat-stress assessment.
- 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
Time-weighted average / noise dose over the work shift.
- OSHA / NIOSH noise 90 dBA: 5 dB exchange rate
- OSHA / NIOSH noise 85 dBA: 5 dB exchange rate
- OSHA / NIOSH noise 85 dBA: 3 dB exchange rate
Peak sound pressure level (C-weighted peak used for impulse-noise limits).
Peak Level (Lpeak): sensors, units, and every standardRespirable particulate ≤4 µm (respirable convention); the fraction reaching the gas-exchange region, used in occupational dust exposure.
PM4 (Respirable): sensors, units, and every standardNitric oxide: a combustion gas and a precursor to NO₂ and ozone.
Nitric Oxide (NO): sensors, units, and every standardHydrogen chloride (HCl), a corrosive acid gas from industrial processes and incineration, and a toxic respiratory irritant.
Hydrogen Chloride (HCl): sensors, units, and every standardHydrogen fluoride (HF), a highly toxic and corrosive gas from aluminum smelting, glass etching, and refining.
- OSHA PEL 3 ppm: Table Z-2
- Cal/OSHA PEL 0.4 ppm: as F
- NIOSH REL 6 ppm: 15-minute
- Cal/OSHA PEL 1 ppm: as F
The setup
How a Monitoring Setup Works
Occupational monitoring combines personal exposure sampling, where a monitor or dosimeter worn in the breathing (or hearing) zone captures what an individual worker actually receives over a shift, with area and real-time monitoring that watches specific hazards and alarms on acute risk. Confined-space entry relies on a continuously running multi-gas monitor. In the recommended configuration below, that is a RAE Systems MultiRAE (CO, H₂S, O₂, and LEL in one instrument) on a Thiamis gateway, set up as an area monitor at a fixed point such as a confined-space entry, a process area, or a loading bay. The MultiRAE keeps its own audible and visual alarm for the people beside it, and Thiamis sends every reading over 4G LTE or the site's Wi-Fi to Environet, which alerts supervisors off site by email, SMS, or webhook. What a worker breathes is still measured by the detector or dosimeter that worker wears; the fixed station documents the area. Gas sensors need regular bump-testing and calibration to stay trustworthy; noise and heat monitors log against workload-dependent limits. The recommended configuration below assembles a confined-space and toxic-gas panel. Use the configurator to choose the gas set and add dust, noise, or heat-stress monitoring for the specific hazards of your operation.
Recommended
best match-
Thiamis connects 1 instrument
A gateway that connects the third-party instruments you choose to the Aethair Platform.
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Carbon Monoxide (CO)Hydrogen Sulfide (H₂S)Combustible (LEL)Oxygen (O₂)RAE Systems (Honeywell) portable gas detectors.
Also measures 8 more
Methane (CH₄)Chlorine (Cl₂)Carbon Dioxide (CO₂)Ammonia (NH₃)Nitric Oxide (NO)Nitrogen Dioxide (NO₂)Sulfur Dioxide (SO₂)VOC (Total) -
Which monitor
The Instruments in This Configuration
A 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.
RAE Gas Detectors
RAE Systems (Honeywell) portable gas detectors.
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
Every reading in Environet as it happens, with alerts by email, SMS, or webhook at the thresholds you set.
Compliance reports
Scheduled or on-demand reports against the standards above or your own limits, as PDF or a secure link.
Dashboards and AI analysis
Live displays for a site or the public, and Noesis answering questions about the data in plain language.
Your data, through the API
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.
Article Library
Reading for Occupational Safety & Industrial Hygiene
OSHA Air Quality Standards 2026: PELs & 29 CFR 1910.1000
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.
Ozone Exposure Limits and Monitoring: OSHA and NAAQS
OSHA's ozone PEL is 0.1 ppm as an 8-hour TWA. How NIOSH, ACGIH, and the 70 ppb NAAQS compare, and why ozone needs short-interval monitoring.
Related solutions
Related Solutions
Oil & Gas / Petrochemical
Fence-line VOC, H₂S, and methane leak detection
Cabin Air Quality
Respirable dust, gases, and blast monitoring
Landfill, Biogas & Odor
Methane, H₂S, and odor complaint response
Questions
Occupational Safety & Industrial Hygiene FAQ
What is the difference between a PEL and a TLV?
A permissible exposure limit (PEL) is the legally enforceable OSHA limit for a substance; a threshold limit value (TLV) is a health-based guideline published by the ACGIH that is often stricter and updated more frequently. Employers must meet the PEL and frequently adopt the TLV as best practice. Both are expressed as time-weighted averages, with short-term and ceiling limits for some substances.
What gases are monitored for confined-space entry?
Oxygen, combustible gas (as % LEL), carbon monoxide, and hydrogen sulfide form the standard four, tested in that order and monitored continuously during occupancy. Additional gases are added for specific process hazards. A multi-gas monitor covers them simultaneously with alarms set to the entry limits.
Is personal or area monitoring better?
They answer different questions. Personal sampling captures an individual worker's actual exposure over the shift and is the basis for compliance with exposure limits. Area and real-time monitoring watch specific locations and hazards and provide immediate alarms. A sound program uses both: area monitoring for control and alerting, and personal sampling for exposure compliance.
How do I set up occupational exposure monitoring?
Start from an industrial hygiene assessment to identify the relevant hazards, then combine the appropriate gas, dust, noise, and heat monitoring (personal and area) with proper calibration. Use the configurator to build a confined-space or toxic-gas panel and add monitoring for the other exposures your operation requires.
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