Carbon Monoxide Gas Safety: OSHA Limits, CO Detectors & Monitoring Guide

July 1, 2026

Learn carbon monoxide safety best practices, OSHA and NIOSH exposure limits, CO gas detector requirements, carbon monoxide monitoring systems, symptoms of CO poisoning, and how to choose the right industrial CO gas detector.

Why Carbon Monoxide Safety Matters?

Carbon monoxide exposure is the most common method of death by poisoning in the world.

The effects of carbon monoxide poisoning are well understood. CO gas competes with oxygen to bind with hemoglobin in the blood leading to a reduction of oxygen in the brain. Even low carbon monoxide levels over long periods can have an impact on brain chemistry.

While the exact short term and long term maximum carbon monoxide levels recommended for safety differ worldwide, the consensus is that:

9 ppm (parts-per-million) is the maximum indoor safe carbon monoxide level over 8 hours
200 ppm or greater will cause physical symptoms and is fatal in hours
800 ppm of CO or greater in the air is fatal within minutes

Carbon Monoxide Poisoning Symptoms by Exposure Level

CO Concentration (ppm)	CO Poisoning Symptoms	Potential Effects/ Exposure Guidance
0-9 ppm	No symptoms expected for healthy individuals	Safe indoor exposure over 8 hours by the EPA and WHO
10-35 ppm	Mild headache or fatigue may occur with prolonged exposure in sensitive individuals	Elevated levels that warrant investigation and improved ventilation
100-200 ppm	Severe headache, dizziness, nausea, impaired judgment	Symptoms can develop within 2–3 hours of exposure
200-400 ppm	Severe headache, confusion, nausea, vomiting	Potentially life-threatening after several hours without intervention
400-800 ppm	Disorientation, collapse, unconsciousness	Can become fatal within 2–3 hours, depending on exposure duration
800+ ppm	Loss of consciousness, respiratory failure, death	Fatal within minutes if exposure continues

Below is an easy to use reference chart for carbon monoxide levels suitable to print.

Carbon monoxide CO levels chart

Download a copy of the chart here (pdf).

Safe Carbon Monoxide Levels by Organization

OSHA Carbon Monoxide Exposure Limits

The Occupational Safety and Health Association OSHA sets standards for working conditions in the US including safe carbon monoxide levels.

The OSHA personal exposure limit (PEL) for CO is 50 parts per million (ppm). OSHA standards prohibit worker exposure to more than 50 parts of CO gas per million parts of air averaged during an 8-hour time period. The 8-hour PEL for CO in maritime operations is also 50 ppm. Maritime workers, however, must be removed from exposure if the CO concentration in the atmosphere exceeds 100 ppm. The peak CO level for employees engaged in roll-on roll-off operations during cargo loading and unloading is 200 ppm.

ASHRAE Carbon Monoxide Exposure Limits

The American Society of Heating, Refrigerating and Air-Conditioning Engineers ASHRAE is a voluntary world-wide organization that sets standards for members focused on building systems, energy efficiency, indoor air quality, refrigeration and sustainability. The ASHRAE Standard 62.1-2016, "Ventilation for Acceptable Indoor Air Quality" agrees with the US Environmental Protection Agency and the World Health Organization limit of 9 ppm over an 8 hour exposure.

NIOSH Carbon Monoxide Levels Exposure Limits

The National Institute for Occupational Safety and Health NIOSH is the US federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. The Occupational Safety and Health Act of 1970 established NIOSH as a research agency focused on the study of worker safety and health, and empowering employers and workers to create safe and healthy workplaces.

NIOSH recommends no more than 35 ppm time weighted average TWA exposure limit. In addition, NIOSH recommends no more than 200 ppm short term exposure limit STEL for 15 minutes.

ACGIH Carbon Monoxide Levels Exposure Limits

The American Conference of Governmental Industrial Hygienists ACGIH is a non-profit organization that advances occupational and environmental health.

The ACGIH recommends a Threshold Limit Value – Time-Weighted Average (TLV-TWA) 50 ppm with a TLV- short term exposure limit of 400 ppm. A TLV-TWA is defined as the concentration of a hazardous substance in the air averaged over an 8-hour workday and a 40-hour workweek to which it is believed that workers may be repeatedly exposed, day after day, for a working lifetime without adverse effects.

EPA Carbon Monoxide Levels Exposure Limits

The United States Environmental Protection Agency EPA sets national ambient air quality standards (NAAQS) under authority of the Clean Air Act (42 U.S.C. 7401 et seq.). NAAQS is applied for outdoor air throughout the country.

The NAAQS standard for carbon monoxide in outdoor air is 9 ppm over 8 hours and 35 ppm over 1 hour not to be exceeded more than once a year.

WHO Carbon Monoxide Levels Exposure Limits

The World Health Organization WHO suggests maximum carbon monoxide levels both in response to their mandate for outdoor clean air and to help countries develop indoor air quality building standards. In indoor environments, space heaters fueled with oil, gas or kerosene, gas stoves, combustion appliances and tobacco smoking are known to cause significant emissions of carbon monoxide. The WHO recommended limits are:

9-10 ppm for no more than 8 hours
25-35 ppm for no more than 1 hour
90-100 ppm for no more than 15 minutes

UL, CSA, ANSI CO Levels Exposure Limits

Underwriters Laboratories UL is the largest and best known independent, not-for-profit testing laboratory in the world. It conducts product evaluations to confirm that the products meet the “UL” standard in electrical safety, fire testing, medical device testing, EMC testing and more.

American National Standards Institute ANSI works in close conjunction with Underwriters Laboratories, and many of the standards are listed as ANSI/UL. UL also has a close association and shares product ratings with the CSA Group which is accredited by the Standards Council of Canada.

The ANSI/UL 2034, ANSI/UL 2075 and CSA 6.19-01 “Standard for Safety for Single and Multiple Station Carbon Monoxide Alarms” requirements are purchased by manufacturers before submitting their devices for testing. They are not normally available to the public. However, UL-certified CO alarms meet a different range of standards that balance the responsiveness of the alarm with the requirement that they not generate nuisance alarms due to background CO caused by outdoor pollution, the normal use of fuel burning appliances or other vapors like methane or ammonia.

The alarm thresholds, set by CO concentration measured in parts per million (ppm), are: no alarm below 30 ppm until after 30 days; 70 ppm for one to four hours (but not less than one hour); 150 ppm for 10 to 50 minutes; 400 ppm for four to 15 minutes.

How to Choose the Right Carbon Monoxide Gas Detector

Selecting the proper carbon monoxide gas detector depends on the application, monitoring requirements, and regulatory standards.

Consider:

Fixed vs. portable CO detectors
Detection range
Audible and visual alarms
Relay outputs
BMS integration
Remote sensors
Calibration requirements
Maintenance intervals
Indoor vs. outdoor installation

Industrial environments often require fixed CO monitoring systems capable of continuous operation and remote alarm notification to protect works and maintain OSHA compliance.

For a popular wall mounted option, CO2Meter offers the Carbon Monoxide (CO) Fixed Gas Detector w/ Remote Sensor (0-50ppm). This device has 3 configurable relays, connects with most Building Management Systems (BMS) and has audible and visual alarms to meet OSHA code compliance thresholds.

Carbon Monoxide Monitoring Systems for Commercial and Industrial Facilities

Carbon monoxide monitoring systems continuously measure CO concentrations and activate alarms when dangerous levels are detected.

These systems are commonly installed in:

Parking garages
Manufacturing plants
Breweries
Beverage facilities
Warehouses
Laboratories
Mechanical rooms
Generator enclosures
Commercial kitchens

Modern gas safety monitoring systems may include:

Multiple CO sensors
Audible alarms
Horn strobes
Building automation integration
Remote monitoring
Relay outputs
Data logging
Network connectivity

Continuous monitoring helps facilities comply with OSHA recommendations while protecting employees from dangerous carbon monoxide exposure.

Carbon Monoxide Safety Best Practices

Because we know that Carbon monoxide (CO) is an odorless, colorless, and toxic gas that can accumulate without warning in residential, commercial, and industrial environments; a comprehensive safety program should be adhered to.

Because CO cannot be detected by human senses, implementing proactive carbon monoxide safety measures is essential for protecting occupants, employees, and visitors from potentially life-threatening exposure. Below is our recommended safety checklist.

Carbon Monoxide Safety Checklist

✔ Install continuous carbon monoxide monitoring systems in areas where CO may accumulate.

✔ Select carbon monoxide gas detectors designed for your specific application, whether residential, commercial, or industrial.

✔ Test carbon monoxide alarms and gas detection systems regularly to verify proper operation.

✔ Calibrate fixed and portable carbon monoxide gas detectors according to the manufacturer's recommended maintenance schedule.

✔ Inspect and maintain boilers, furnaces, water heaters, generators, ovens, and other fuel-burning equipment to reduce CO emissions.

✔ Ensure ventilation systems are operating correctly to prevent dangerous carbon monoxide buildup.

✔ Train employees on carbon monoxide hazards, symptoms of CO poisoning, emergency response procedures, and evacuation protocols.

✔ Document inspections, maintenance, calibration records, and employee safety training to support regulatory compliance.

✔ Follow OSHA regulations, local fire codes, manufacturer recommendations, and applicable industry standards when designing and maintaining carbon monoxide monitoring systems.

By combining reliable CO gas detection systems with routine inspections, preventative maintenance, and comprehensive safety training, organizations can minimize the risk of carbon monoxide exposure, maintain compliance with workplace safety standards, and create a safer environment for everyone.

Frequently Asked Questions about CO Safety

What level of carbon monoxide is dangerous?

Carbon monoxide becomes hazardous as concentration and exposure time increase. According to OSHA, the permissible exposure limit (PEL) is 50 ppm averaged over an 8-hour workday. NIOSH recommends an even lower time-weighted average of 35 ppm. Concentrations above 200 ppm can quickly produce headaches, dizziness, nausea, and other symptoms, while 800 ppm or more can become fatal within minutes. View this article on the differences between CO2 vs. CO dangers.

What does a carbon monoxide detector detect?

A carbon monoxide detector continuously measures carbon monoxide gas concentrations in the surrounding air. Industrial CO gas detectors provide real-time monitoring, visual and audible alarms, relay outputs, and Building Management System (BMS) integration to alert personnel before hazardous exposure occurs.

Where should carbon monoxide detectors be installed?

Carbon monoxide detectors should be installed anywhere combustion equipment or fuel-burning appliances are present, including:

Mechanical rooms
Boiler rooms
Generator rooms
Parking garages
Warehouses
Laboratories
Manufacturing facilities
Loading docks
Commercial kitchens

Installation height should follow the manufacturer's recommendations and applicable local codes.

What causes carbon monoxide buildup?

Common sources include:

Gas furnaces
Boilers
Water heaters
Vehicle exhaust
Propane-powered forklifts
Gas generators
Natural gas appliances
Wood-burning equipment
Fireplaces

Poor ventilation can significantly increase CO concentrations.

References: