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Civil Engineering

General Chemical Hazards

5.1 Corrosivity

Corrosive chemicals cause visible destruction or irreversible alteration to living tissue. Common acids and bases are the most usual corrosives encountered, but other chemicals such as Br2 are also extremely corrosive.

  • concentrated acids and bases should always be diluted by addition to water due to the large heat of solution for these compounds
  • use appropriate personal protective equipment and fume hood ventilation when working with strong acids and bases, and other corrosive substances
  • safety glasses do not provide complete eye protection from chemical splashes; wear appropriate safety goggles or splash shields when working with corrosive substances

NOTE: some specific acids such as HF (extremely toxic) and HClO4 (powerful oxidizer of organics) require special handling procedures. Consult the appropriate references and your supervisor before working with these chemicals.

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5.2 Flammability

The risk of fire in the chemical laboratory is most often associated with two classes of compounds - common organic solvents, and certain metals, metal hydrides and organometallics. For common organic solvents the following should be noted:

  • the minimum temperature at which vapours from a substance will ignite when exposed to an ignition source (flame, spark, static discharge, etc.) is called the flash point
  • a flammable substance has a flash point below 40¬∞C
  • a combustible substance must be heated above 40¬∞C to ignite
  • up to 1L glass bottles of flammable liquids can be stored anywhere in laboratories; larger quantities must be stored in flammable storage cabinets (e.g. 4L glass bottles) or in approved safety containers
  • the maximum volume of flammable liquids that may be stored in a laboratory is 225 litres
  • always use ventilation (e.g. fume hoods) which is adequate for the quantity of flammable liquid in use; only use fume hoods which have been designated and labelled for use with flammable liquids
  • always connect (or bond) containers when transferring flammable liquids from metal containers
  • NEVER store flammable liquids in a conventional domestic refrigerator; only refrigerators/freezers that are approved for flammable storage can be used

Alkali and alkaline earth metals, certain other metals such as aluminium, metals in a finely divided form, metal hydrides and many organometallic compounds can ignite on exposure to air and/or water. The following should be noted when working with this class of compounds:

  • store these chemicals in a location separate from other chemicals in the laboratory and in containers appropriate for the purpose
  • use equipment appropriate for the hazards associated with these substances including inert atmosphere techniques
  • class "D" fire extinguishers (metal fires) must be present in laboratories where these substances are in use; do not use "C" class fire extinguishers (CO2) on metal fires
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5.3 Noxious Chemicals

Certain classes of compounds such as thiols (mercaptans) and related sulfur-containing compounds are characterized by a particularly noxious odour

  • these compounds must be used with adequate ventilation (fume hoods)
  • whenever compounds of this type are used they will be released through the ventilation system into the local atmosphere, consequently both the Department Safety Officer and the Emergency Report Centre must be notified in advance of the use of these chemicals
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5.4 Reactive Chemicals

Air/Water Reactive

chemicals which can ignite on exposure to air or water, e.g. certain metallic and organometallic substances, phosphorous

special handling, storage and disposal procedures must be established in laboratories where these substances are in use (see section on Flammability and Appendix II - Incompatible Chemicals)

Self-Reactive Chemicals

may be heat, shock or friction sensitive and can react violently as a consequence, e.g. acetylene and acetylides, azides, diazonium salts, nitro compounds, chlorates and perchlorates, peroxides

special handling, storage and disposal procedures must be established in laboratories where these substances are in use

labs must remain closed and locked when not in immediate use

Lachrymators

substances which react with moisture in the eyes and mucous membranes to cause tear formation, e.g. halogenated aldehydes, ketones and esters

must be used with adequate ventilation (fume hood) and stored in well sealed containers

Incompatible Chemicals

Accidental contact of incompatible chemicals can lead to fire, explosion and/or the release of highly toxic substances. The magnitude of the problem usually increases with the quantity of chemicals being stored. Prudent practice requires that incompatible chemicals be stored in separate locations to minimize the risk of accidental mixing. Appendix II - Incompatible Chemicals lists some general groups of incompatible chemicals; further information on specific chemicals may be obtained from references such as Hazards in the Chemical Laboratory, by L. Bretherick or Prudent Practices in the Laboratory: Handling and Disposal of Chemicals, National Research Council, National Academy Press, 1995.

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5.5 Toxicity

A wide range of substances are present in the chemical laboratory which present a risk due to either chronic or acute toxicity; this includes the presence of carcinogens, mutagens and teratogens:

  • toxic substances may enter the body by inhalation, absorption, ingestion and/or injection
  • appropriate protective measures must be taken to prevent exposure and which are consistent with permissible exposure limits for a specific substance
  • where available, antidotes for poisons must be present during usage of these poisons

NO FOOD OR DRINKS ARE TO BE CONSUMED IN LABORATORIES AT ANY TIME.

CONTAINERS/UTENSILS USED FOR THE PREPARATION OR CONSUMPTION OF FOOD OR BEVERAGES MUST NOT BE STORED IN LABORATORIES WHERE HAZARDOUS SUBSTANCES ARE IN USE.

ANY WOMAN WHO WORKS IN A LABORATORY WHERE HAZARDOUS SUBSTANCES ARE IN USE AND WHO IS, OR BELIEVES THAT SHE MAY BE, PREGNANT MUST INFORM HER SUPERVISOR.

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5.6 Designated Substances

The Occupational Health and Safety Act allows a biological, chemical or physical agent, or combination thereof, to be "designated" and its use in the workplace may be either prohibited or strictly regulated. The following are designated substances:

  • ACRYLONITRILE
  • ASBESTOS
  • BENZENE
  • CARBON DISULFIDE
  • CARBON TETRACHLORIDE
  • COKE OVEN EMISSIONS
  • ETHYLENE OXIDE
  • ISOCYANATES
  • LEAD
  • MERCURY
  • SILICA POWDER
  • STYRENE
  • VINYL CHLORIDE MONOMER

Acrylonitrile, benzene, carbon disulfide, carbon tetrachloride, isocyanates, styrene, and vinyl chloride monomer are all volatile organic materials and must be used with adequate ventilation (fume hood) to prevent exposure through inhalation and with appropriate protective equipment to prevent exposure through skin absorption. These materials can be disposed of in the normal liquid organic waste stream (halogenated or nonhalogenated as appropriate).

Substances containing arsenic, lead or mercury must be handled in an appropriate manner to prevent exposure through inhalation or absorption. All chemical waste containing arsenic, lead or mercury must be collected and properly labeled for disposal by the Department of Environmental Health and Safety.

Elemental mercury is used in many types of apparatus, in particular mercury-filled thermometers. Mercury spills from broken equipment should be cleaned up immediately (mercury spill kits are available from the Department of Environmental Health and Safety). Broken thermometers are collected by the Environmental Technologist who will recover the mercury from the thermometers before disposal.

Silica powder, including chromatography grade silica, is a respiratory hazard and should be handled in a fume hood when dry. Any fine silica sand (normally found at the Coastal Laboratory) would have a certain amount of powder and should be handled wet and otherwise be covered. Used silica should be stored in sealed and labelled containers then sent for disposal by the Department of Environmental Health and Safety.

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