Characteristics of Hydrogen
- People working with hydrogen should understand its basic characteristics:
- Colorless, odorless, and non-toxic
- Propensity to leak – can diffuse through many materials considered airtight or impermeable to other gases
- Buoyant – hydrogen is the lightest gas; will rise quickly under atmospheric conditions, can accumulate at the ceiling
- Flammable – when mixed with air can result in flames or explosions
- Burns with an invisible flame and gives off little radiant heat
- Can cause hydrogen embrittlement in metals, leading to component failure
- See So you want to more about Hydrogen for more details.
Before laboratory operations are begun, evaluations should be done to identify specific hazards and a Safety Plan should be developed and reviewed. See Safety Planning for a recommend formal evaluation process. Evaluations should include consideration of:
- Hydrogen reactivity with other chemicals in the process
- Properties and reactivity of intermediates and end products that might be formed
- Catalysts and materials with catalytic-like properties
- Operation of the equipment at the operating conditions
- See Chemical and Metal Hydride Hydrogen Storage for more information of their specific hazards
Entering the Laboratory
Human senses cannot readily detect the presence of hydrogen gas and may not easily detect a hydrogen flame. Even though substantial thought may have gone into a system design to benefit safety, personnel approaching laboratories or equipment containing hydrogen should confirm that neither a flammable mixture nor hydrogen fire is present.
It is difficult with our human senses to have ready awareness of small quantities of released hydrogen gas or a hydrogen fire. Hydrogen is colorless, odorless, burns with a nearly invisible flame (especially during daylight hours), and gives off relatively little radiant heat. Even though substantial thought may have gone into a system design to benefit safety, personnel approaching laboratories or equipment containing hydrogen should confirm that a flammable mixture or hydrogen fire is not present.
- Before entering the proximity of hydrogen-containing laboratories or equipment, consult the status of fixed gas sensors and flame detectors.
- Always use the prescribed personal protective equipment (PPE) before attempting to operate hydrogen-containing equipment.
- If fixed sensors and detectors are not installed, thermal imaging cameras can verify that a hydrogen flame is not present. If a flame is not present, confirm with a personal gas detector that flammable mixtures are not present.
- If these tools are not available, personnel should assume a leak. Watch for thermal waves that signal the presence of a flame. Use a long combustible object (e.g., a broom) to probe for the presence of a suspected flame. Certain environments such as salt air found near the ocean, will produce a blue-tinted flame due to the presence of sodium.
Although hydrogen fires do not produce smoke themselves, burning of nearby combustible materials can result in smoke.
Laboratories containing hydrogen may be at risk of an explosion hazard and should rely on a combination of hydrogen containment, purging operations, ventilation, and ignition source control to prevent an explosion. The types of preventive measures used depend on the amount of hydrogen present, the hydrogen pressures, and the nature and amounts of other flammable materials or oxidizers in the lab. See Hydrogen Explosions for more information about explosions.
Verifying the operability of systems that prevent or mitigate explosion hazards such as leak detection and ventilation should be done before operations begin. If explosion protection shields are employed, the condition of such shields should also be verified.