Episode 44 introduces the chemicals most frequently covered under OSHA’s Process Safety Management (PSM) Standard (29 CFR 1910.119). Dr. Ayers explains why certain chemicals are regulated, what makes them hazardous, and how their properties influence process safety requirements.
The core message: PSM chemicals are dangerous because of their potential for catastrophic consequences — fire, explosion, or toxic release. Understanding their hazards is the first step in controlling them.
OSHA regulates chemicals under PSM because they have one or more of the following characteristics:
Highly toxic
Highly reactive
Highly flammable
Capable of rapid energy release
Able to form explosive mixtures
Dangerous even in small quantities
These chemicals can cause mass casualties, major property damage, and community‑scale impacts if released.
Episode 44 groups the most common PSM chemicals into several hazard categories.
These chemicals can cause severe injury or death at low concentrations.
Examples include:
Chlorine
Phosgene
Hydrogen sulfide (H₂S)
Anhydrous ammonia
Hazards include respiratory failure, pulmonary edema, and rapid incapacitation.
These chemicals can ignite or explode when mixed with air.
Examples include:
Propane
Butane
Ethylene
Hydrogen
Acetylene
Flammables are the most common PSM‑covered chemicals because they are widely used in industry.
These chemicals can undergo violent reactions if mixed, heated, or contaminated.
Examples include:
Peroxides
Organic nitrates
Polymerizable monomers
Water‑reactive metals
Reactivity hazards often lead to runaway reactions and vessel overpressure.
These chemicals can release large amounts of energy rapidly.
Examples include:
Hydrogen peroxide (high concentration)
Ammonium nitrate
Certain oxidizers
These materials require strict control of temperature, contamination, and confinement.
While not always acutely toxic, corrosives can damage equipment and lead to secondary failures.
Examples include:
Sulfuric acid
Hydrochloric acid
Sodium hydroxide
Corrosion is a major contributor to mechanical integrity failures.
Dr. Ayers emphasizes that PSM chemicals are dangerous not just because of their inherent hazards, but because of:
Quantity stored
Process conditions (pressure, temperature)
Potential for rapid release
Proximity to workers and communities
A small amount of a highly toxic chemical can be just as dangerous as a large amount of a flammable one.
Many catastrophic events involving PSM chemicals share similar causes:
Loss of containment
Overpressure events
Runaway reactions
Improper mixing
Equipment failure
Human error during startup or shutdown
Inadequate hazard communication
Understanding the chemicals helps prevent these failures.
Chemical properties directly influence:
PSI — hazard data must be accurate
PHA — scenarios depend on chemical behavior
Operating Procedures — limits and steps reflect chemical hazards
Training — workers must understand chemical risks
Mechanical Integrity — materials of construction depend on corrosivity and reactivity
Emergency Planning — response depends on toxicity and flammability
Chemical knowledge is the foundation of process safety.
Safety leaders must:
Ensure chemical hazard information is complete and current
Train employees on the specific hazards of PSM chemicals
Verify that safeguards match the chemical risks
Integrate chemical properties into PHAs, procedures, and MI programs
Communicate hazards clearly to contractors and responders
The episode’s core message: You cannot manage process safety if you don’t understand the chemicals.
