Any chemical used in a laboratory should be handled with care and according to laboratory procedures. Before performing work involving chemicals, safe handling procedures and the chemical's Safety Data Sheets (SDS) must be reviewed. If mixing chemicals, the reactivity of each must be reviewed to avoid adverse chemical reactions. Chemicals are hazardous for many reasons.


Toxic substances

Many chemicals used in laboratories may be toxic. Toxicity depends on the quantity, frequency and duration of exposure, or the dose. Toxic effects can be local (at the site of exposure) or systemic (at another site in the body), acute or chronic. When dealing with toxic chemicals, it is important to consider the route of exposure and the target organ to ensure that proper controls are adhered to.

When planning and conducting experiments, it is critical to recognize that the combination of toxic effects of two or more substances may be significantly greater than that of one substance alone. Toxic reaction products can be much more dangerous than the starting reagents. Many cases of toxic reaction products occur when chemicals are mixed unintentionally. This can occur due to improper labelling, mishandling of chemicals and spills.

Laboratory workers must be able to recognize the potential hazards present to prevent exposure to toxic chemicals, and in the event of accidental exposure, know the procedures for emergency, spill response and first aid.

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Flammable liquids

A maximum of 300 L of combustible (class II and III) and flammable liquids (class I), of which no more than 50 L can be flammable (class I), can be outside of a flammable liquid storage cabinet at any one time.

A maximum of 500 L of combustible (class II and III) and flammable liquids (class I), of which no more than 250 L can be flammable (class I), can be stored in an approved flammable liquid storage cabinet. Each lab is permitted a maximum of 3 flammable liquid storage cabinets.

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Oxidizing agents represent a significant hazard in the laboratory due to their capacity to undergo violent reactions when they come into contact with reducing agents, causing ignition in flammable and combustible materials. Oxidizers can also increase the intensity of a small fire, making safe storage a key consideration in the lab. In addition to the risk of fire, oxidizers may release toxic gases either by reacting with other chemicals, or through decomposition caused by heating. Oxidizers on their own can also have corrosive properties.

Oxidizers may be found in both solid and liquid form. Solid oxidizing agents such as metallic chlorates, perchlorates, nitrates, chromates and permanganates may form explosive mixtures with oxidizable dusts and other suspended particles (e.g. flour, coal dust, magnesium powder, zinc dust, carbon powder).

Liquid oxidizers include nitric acid, chromic acid and sulphuric acid. In addition to being oxidizers, these are also corrosive chemicals. One of the most hazardous liquid oxidizers is perchloric acid, and should be avoided if possible. If perchloric acid must be used, workers must be trained in safe handling procedures and a perchloric acid fume hood designed and constructed for this purpose must be used.


Corrosive materials include chemicals that will result in an immediate, acute erosive effect on tissue as well as other materials. Corrosive chemicals include strong acids and bases, dehydrating and oxidizing agents, and halogen gases.

When handling corrosive chemicals, the eyes and skin are most commonly at risk, however failure to use proper protective equipment and handling procedures can result in exposures to the respiratory and digestive tract through inhalation and ingestion as well.

Corrosive chemicals exist in solid, liquid and gaseous forms. Some examples and their effects are:

Corrosive solids Sodium hydroxide, phosphorous, phenol. Dust from these can be inhaled and cause serious damage to the respiratory tract.

Corrosive liquids - Bromine, sulfuric acid, aqueous sodium hydroxide, hydrogen peroxide. The danger in liquid form is the speed at which the liquid reacts upon contact, causing immediate destruction of tissue.

Corrosive gases - Chlorine, ammonia, nitrogen dioxide, hydrogen chloride, formaldehyde. Exposure occurs through inhalation, causing damage to the lining of the respiratory tract and lungs.

Special consideration must be given to the use of hydroflouric acid or hydrogen flouride. It should be avoided if at all possible, and if used, workers must be trained in safety procedures, first aid, and spill response. Specific procedures for hydrogen flouride are below.

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Highly reactive chemicals

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Ethidium bromide handling procedures

  1. Consult the Material Safety Data Sheet on ethidium bromide before using the chemical.
  2. Wear personal protective equipment when handling ethidium bromide.
    • Lab coat
    • Nitrile gloves
    • Closed toe shoes
    • Splash Goggles
    • Eye wash/deluge shower
  3. Leave personal protective equipment in laboratory.
  4. Work with ethidium bromide in a designated area.
  5. Equipment used with ethidium bromide should be designated as such and not used for other work unless decontaminated.
  6. A UV light may be used to detect the presents of ethidium bromide, remember to use appropriate protective equipment when using UV lights.

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