IDLH – Immediately Dangerous to Life and Health

PEL – Permissible Exposure Limit

STEL – Short-Term Exposure Limit

TLV – Threshold Limit Value.

The Occupational Safety and Health Administration (OSHA) uses these terms to define exposure limits and establish guidelines for workplace safety. OSHA mandates that every employer must provide a safe and healthful workplace—even when hazardous materials are present. There are hundreds of toxic substances in regular industrial use, many of which are odorless, colorless, and undetectable without the proper equipment. That’s why toxic gas monitoring systems are critical to provide early warning, protecting personnel and property. Life Safety and Hazardous Material Emergency Alarm Systems are the last line of defense against these invisible threats in the workplace.

One of the most widely used hazardous chemicals is ammonia—a colorless gas with a pungent, irritating odor. Lighter than air and highly reactive, ammonia is a building block for many industrial, agricultural, and pharmaceutical products. It is also a common ingredient in cleaning supplies. Ammonia leak detection is critical in two high-risk applications: in agriculture, where ammonia is used in its anhydrous form (without water), and in industrial refrigeration, where ammonia is employed as a highly efficient cooling agent.

Refrigerants, such as fluorinated hydrocarbons (commonly known by the trade name “Freon”), are used extensively in HVAC systems and industrial refrigeration. Gases like difluorodichloromethane are colorless, with faint odors, and typically stored as liquids under pressure. These substances are non-flammable but can cause frostbite on contact and displace oxygen, creating serious asphyxiation hazards. HVAC technicians and service professionals may experience routine low-level exposure to refrigerants, which is often harmless. However, in confined spaces, leaks can rapidly cause headaches, nausea, vomiting, and in extreme cases, loss of consciousness or death. Early refrigerant leak detection is essential to protect workers in these environments.

Carbon Monoxide is an invisible, odorless gas that can cause sudden illness and death if inhaled. Carbon Monoxide has a density about the same as air and is created by numerous combustion processes. For example, Carbon Monoxide is a common workforce hazard for employees who work around vehicle exhausts, fuel-burning furnaces, coal-burning power plants, and forklifts. Additionally, propane-powered heaters, gas water heaters, and kerosene heaters can all produce Carbon Monoxide. All facilities with these combustion applications should evaluate their processes to determine if CO leak detection is required to insure employee safety. In many countries, carbon monoxide is the most common cause of fatal air poisoning.