Civil Engineering

Safe Laboratory Procedures and Techniques

4.1 Glassware

  • check glassware for cracks, chips and other flaws; these flaws should be repaired before the glassware is used
  • select the right glassware for the job; vacuum applications required thick-walled glass while operations carried out under pressure require specially designed glassware
  • glassware under pressure or vacuum should be shielded
  • if it is necessary to apply pressure to glassware, wear thick leather gloves
  • never heat or apply pressure/vacuum to a chemical in a stock bottle; these bottles are made of a soft glass which breaks readily
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4.2 Electrical Equipment

In addition to the hazards posed by electrical shock, electrical equipment also presents a source of fire hazard when used in conjunction with flammable substances (see section on Flammability). Electrical hazards can be minimized by the following:

  • only trained or qualified individuals should repair or modify electrical equipment electric wires should never be used as supports
  • unplug equipment by pulling on the plug not the cord
  • equipment should be regularly inspected and frayed cords or broken plugs should be repaired
  • any equipment failure or overheating should be remedied immediately
  • use "C" class fire extinguishers for electrical fires
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4.3 Static Electricity and Spark Hazards

Protection from static discharge must be addressed in particular when handling flammable solvents; this risk is increased during periods of low humidity. Proper grounding of containers and equipment will significantly reduce this risk. Common potential sources of sparks and static discharges are:

  • ungrounded metal tanks and containers
  • clothing or containers made of plastic or synthetic materials
  • high pressure gas cylinders upon discharge
  • control systems on hotplates
  • brush motors and forced air dryers
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4.4 UV Lamps

Radiation of wavelengths below 250 nm poses a considerable risk to both eyes and exposed skin. Wear UV-absorbing safety glasses and avoid direct eye contact with the UV source; wear protective clothing to prevent burns from UV exposure. Work involving UV irradiation should be carried out in an enclosed work area to prevent exposure of workers to the UV source.

Mercury arc lamps should be cleaned thoroughly before use. Handling with bare hands leaves oil deposits on the surface of the outer glass which forms residues that will burn into the glass causing build-up of heat during the operation of the lamp. The lamp may overheat and crack, releasing mercury vapour as a consequence.

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4.5 Lasers

The type and intensity of radiation available from a laser varies greatly from one instrument to another. The following general rules should be followed:

  • always wear goggles that offer protection against the specific wavelength(s) of the laser in use; no available goggles protect against all laser wavelengths
  • never look directly at the beam or pump source
  • never view the beam pattern directly; use an image converter or other safe, indirect means
  • do not allow objects that cause reflections to be present in or along the beam
  • keep a high general illumination level in areas where lasers are in operation; low levels of light cause dilation of the pupils, thereby increasing the danger to the eyes
  • display warning signs
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4.6 X-ray Generators

X-rays are a hazardous physical agent under the Occupational Health and Safety Act. Any equipment generating X-rays must be operated in accordance with government regulations and appropriate warning signs must be posted.

4.7 Magnetic Fields

NMR spectrometers have superconducting magnets which generate static magnetic fields with high flux densities. Hazards exist from the mechanical forces exerted by these magnetic fields on ferromagnetic tools and equipment and on medical implant devices. Individuals with implanted cardiac pacemakers and similar medical devices should not be exposed to these magnetic fields. Other implanted medical devices such as suture staples, aneurysm clips, prostheses, etc. may also be subjected to adverse effects.

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4.8 Radioactive Material

All work involving the use of radioactive materials must be carried out under the supervision of a faculty member who is licensed by the Atomic Energy Control Board to work with radioisotopes.

Radiation badges are to be worn while using any radioactive instrument. All work must be approved by the Civil Technologist or the Departmental Manager before it is carried out. All radioactive materials must be handled, stored and disposed of in accordance with the appropriate government regulations and in accordance with procedures set out by the Department of Environmental Health and Safety, Queen's University (see the Waste Disposal section - Radioisotope Disposal Procedures).

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4.9 Compressed Gases

Gases used in laboratories are supplied in cylinders at high pressure. In addition to any potential chemical hazards, compressed gases are a high-energy source and therefore hazardous. The following rules must be followed:

  • cylinders of all sizes must be restrained from falling by restraining devices
  • during storage or transport, the cylinder cap must be in place
  • cylinders must only be transported when strapped to a wheeled cart
  • no lubricant shall be used when connecting the regulator to the cylinder
  • new connections shall be checked for gas leakage
  • the cylinder delivery pressure shall be set to zero after the main cylinder valve is closed to prevent a rapid release of compressed gas the next time the cylinder is opened
  • empty cylinders shall have the regulators removed, be marked MT, the shipping cap replaced and returned to main storage in room 024
  • unused or partially used cylinders that are of no further use shall be returned to gas company
  • in the event of a fire, the supply of a combustible gas shall be shut off before any attempt is made to extinguish the flame
  • a trap shall be used to prevent the back siphoning of solution when a soluble gas is being employed
  • do not expose cylinders to temperatures higher than 50¬∞C
  • use toxic, flammable or reactive gases in a fume hood
  • use the appropriate regulator for the type of gas
  • be aware that special handling procedures are required for certain gases, e.g. acetylene
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4.10 Cryogenics and Cold Traps

Liquid nitrogen is the most common cryogenic coolant and must be handled with caution. The following points must be taken into account when using liquid nitrogen

  • use only a properly vented container
  • extreme cold can rapidly cause tissue damage; use appropriate protective equipment
  • spills in confined spaces can cause asphyxiation due to rapid evaporation of the nitrogen
  • glass Dewars used as cold traps should be encased to contain glass fragments in the event of implosion
  • do not leave liquid nitrogen cold traps open to the air; oxygen may condense from the air and can react explosively with combustible materials

Dry ice is frequently used in conjunction with a cooling liquid. These cooling systems can also cause tissue damage due to extreme cold. The proper choice of a cooling liquid presents problems since a non-toxic, non-flammable, low viscosity, low volatility liquid does not exist. In general isopropanol (flash point 11°C) is preferable to acetone (flash point -18°C) due to a higher flash point but still represents a fire hazard. A 3:2 mixture of ethylene glycol to water which is thinned with isopropanol is an alternative cooling liquid with reduced flammability.

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4.11 Reduced Pressure Operations and Vacuum Pumps

  • vacuum desiccators should be taped or encased due to the risk of implosion
  • glass vacuum lines should be shielded when in use
  • cold traps should be placed between apparatus and vacuum pumps to prevent volatiles from entering the pump oil; traps should be cleaned after use
  • exhaust from the pump should be vented into a fume hood or to the exterior of the building; exhaust must be vented in a manner that prevents contact of the emissions with the public (i.e. must not be vented at ground level)
  • pump belt drives must have a guard over the belt to prevent anything from getting caught in the belt
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4.12 Distillations and Reflux Operations

Distillations and reflux operations are common laboratory procedures which present several potential dangers: pressure build-up leading to explosions if closed systems are used, and fire hazards associated with heating flammable substances are two of the most common. A variety of apparatus designs are available to accomplish reflux/distillation operations at atmospheric pressure, under inert atmospheres, under reduced pressure and by the addition of steam. The following general points should be noted when carrying out these operations:

  • check the integrity of the system; leaks of flammable materials can lead to fires
  • ensure smooth boiling through stirring or the addition of boiling stones (do not add boiling stones to hot liquid)
  • choose an appropriate heat source - electric heating mantle, ceramic cavity heater, steam bath or silicone oil bath
  • do not heat the heat source above their auto-ignition temperature of the liquid being distilled/refluxed
  • do not distill organic liquids to dryness
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