Hydrofluoric acid (HF) is extremely hazardous. Unlike most other acids, HF can penetrate quickly deep into tissue and bones. It reacts with calcium ions in the body, causing electrolytic damage and severe, deep pain despite minimal surface damage. Exposures to as little as 2% of the body have been reported to cause death.

Protective equipment is your best defence when working with HF.

If exposed...

immediately flush exposed skin with water
remove contaminated clothing
liberally apply calcium gluconate gel to the area
tell your supervisor and get immediate emergency medical treatment

Chemical hazards fall largely under the umbrella of McMaster University's Hazardous Materials Management Program, as outlined in RMM #501.

Hazardous chemicals, as defined in the LSH, can be:

explosive
flammable/combustible
reactive
oxidizing
toxic
corrosive (ph < 5.5 or > 9.5)
compressed gas

In Canada, anyone working with hazardous materials is required to take Workplace Hazardous Materials Information System (WHMIS) training. WHMIS is considered mandatory training for all persons working in Eng Phys or the CEDT.

All chemicals must be properly labelled in accordance with WHMIS standards. A catalogue of Material Safety Data Sheets (MSDSs) must be maintained for any location where chemicals are stored.

Explosive materials

Explosive materials produce almost instantaneous release of pressure, gas, and heat when subjected to sufficient shock, pressure, or temperature.

Flammables/Combustibles

This class of materials ignites and burns readily.

Flammables have a flashpoint below 37.8°C. Combustibles have a flashpoint at or between 37.8°C and 93.3°C. The flashpoint is the temperature at which the material produces enough vapour to allow ignition and burning.

At high enough temperatures certain flammable or combustible materials can spontaneously autoignite. No flame or similar ignition source is required.

Reactive materials

This class of materials tends to react when mixed with certain other materials, potentially generating or absorbing heat, and creating chemical bi-products.

Proper storage of reactive materials and waste products with only compatible materials is critical, as the presence of incompatible chemicals could result in harmful bi-products, heat, fire, or explosion.

Oxidizing materials

Oxidizing materials can cause or promote combustion of other materials. Oxidizers can be materials rich in oxygen, like chlorates and permanganates, or materials that promote oxidation, like chlorine or bromine, by incorporating excess electrons from the oxidation process.

The presence of oxidizing liquids or solids increases risk of ignition and explosion. Certain materials that are normally non-flammable may burn in the presence of oxidizers.

Toxic materials

Toxic materials react harmfully with organic tissue. If exposed to sufficient doses, tissue damage may be irreparable.

Routes of entry for toxic materials may be through the skin, or via ingestion or inhalation.

Corrosive materials

Corrosive materials, typically acids or bases, chemically attack and damage other materials that they contact.

Corrosives can damage organic tissue on contact. Stronger corrosives attack tissue more rapidly.

Ingestion or inhalation of corrosives or their vapours can burn sensitive digestive or respiratory tissues.

Compressed gases

Compressed gases are stored under pressure in cylinders, or sometimes in pressurized transport lines. They can be categorized as liquefied, non-liquefied, or dissolved.

The high pressures associated with compressed gases poses a hazard in the event that a tank leaks or ruptures, as the pressure can be sufficient to propel the tank at high velocity. As such, gas cylinders need to be securely attached to wall-mounted or table-mounted brackets. Cylinders must be capped and secured in a transport cart when relocated.

Compressed gases often pose additional hazards insofar as they may be reactive, flammable, oxidizing, or corrosive when released. Safety measures specific to the particular hazard should be put in place.

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Sources:
1. The Canadian Centre for Occupational Health and Safety, http://www.ccohs.ca/oshanswers/chemicals/, October 18, 2005.
2. WHMIS Pocket Dictionary, J. Mayo and D.B. Morris, Genium Group, 2004. Available from EOHSS.