ASSEMBLY AND APPARATUS

This section provides general guidance for the safe design and operation of laboratory apparatus.


Introduction

Hazard” and “Risk” are not the same. A “hazard” is an inherent chemical or physical characteristic that has the potential for causing damage to people, property, or the environment. A hazard can be eliminated, but not reduced. A hazard causes harm. “Risk” is the probability that a hazard will cause harm. It is a is a measure of human injury, environmental damage, or economic loss in terms of both of the “likelihood” and the “magnitude” of the loss or injury. Risk associated with a hazard can be reduced.

There are many ways to identify and evaluate safety hazards in a laboratory. No matter what method or combination of methods you choose, they all help you achieve hazard identification, which will inform your risk assessment and selection of control measures. To conduct a hazard assessment, you should:

  1. IDENTIFY HAZARDS – a review of the materials, equipment, facility, and work habits and practices will reveal potential hazards. The question to ask is “What exactly is the hazard?”
  2. ANALYZE THE RISKS -Rank hazards by how likely they are to happen and how severe the outcomes would be. Questions to ask are “What can go wrong and how?”, “How bad can it be?”, and “How often can it happen? “
  3. SELECT CONTROLS -Choose the best possible response to eliminate a hazard or lower its risk of occurring. The question to ask is “How do we control and manage this given the risk?”

Safe Design and Assembly of Apparatus

  • Prior to new equipment set-up, a Hazard Review Checklist (Appendix F) should be completed to determine if adequate safety plans were considered in your equipment design. The completed checklist is to be reviewed and approved by your faculty advisor prior to the initiation of an experiment.

 

  • You may choose to use more than one method beyond the Hazard Review Checklist for your lab’s hazard identification and evaluation assessment. The American Chemical Society has developed a full suite of hazard identification tools. Other examples can be found in SECTION XIII under key references.

 

Safe Operation of Apparatus

  • Procedures that may release toxic vapors, fumes, mists, or aerosols should be performed in a chemical fume hood or other local exhaust ventilation device.

 

  • The apparatus should be set up in a clean and dry area. Be certain that the equipment is firmly clamped and is kept well back from the edge of the laboratory bench. Many accidents occur when someone walks by a bench and brushes against the glassware or other equipment.

 

  • Make sure that you use the proper size equipment for the experiment, allowing at least 20% free space. Flasks that contain solutions to be refluxed should have 50% free space.

 

  • Bunsen burners are allowed in laboratories provided the immediate areas around them are kept clear of combustible and flammable materials. A good rule of thumb is a ~1-foot radius clearance with an additional ~2-foot radius work zone that is clear of flammable/combustible materials that are not immediately needed for the work being done. It is especially important for labs to maintain clear access to designated exits and know where fire extinguishers are. Beware of the quiet and nearly invisible nature of a Bunsen burner flame. Open flame work beyond the scale of a Bunsen burner must be reviewed and approved in advance by EHS.

 

  • Distillation and other hot operations should be performed with a heating mantle or hot plate only. For routine purification needs, cold solvent filtration systems are greatly preferred over hot distillation; contact EHS for advice.

 

  • To the extent possible, place laboratory balances or scales in low pedestrian traffic areas of the laboratory, away from doors and overhead supply air grilles to minimize air disturbances.

 

  • Position and clamp reaction apparatus thoughtfully to permit manipulation without the need to move the apparatus until the entire reaction is completed.

 

  • Ground glass joints or stopcocks should be sleeved with Teflon or freshly lubricated unless a lubricant will contaminate the system. Retainer rings should be used on stopcock plugs.

 

  • Condensers must be properly supported with securely positioned clamps. Any attached water hoses should be clamped with clamps of an adequate material. Condensers running unattended overnight should preferably be attached to a water pressure regulator in order that surges in the water pressure do not cause the hoses to rupture.

 

  • Stirrer motors should be secured to retain proper alignment. An air driven stirrer or magnetic stirrer should be used whenever possible. Only non-sparking motors ought to be used in hazardous areas, where significant amounts of flammable gases and solvents are present.

 

 

  • If a cooling bath is required and ice water is not cold enough, dry ice in an organic liquid should be used instead of liquid nitrogen whenever possible. The ideal cooling liquid for a dry ice bath should be relatively non-toxic, non-viscous, non-flammable, non-volatile, insoluble in water and should float dry ice. Ethylene glycol thinned with 2/3 water or isopropanol makes a useful cooling mixture.

 

  • Electrical equipment including variacs, stirrers, vacuum pumps, etc., must be carefully checked for faulty or frayed line cords. Grounded electrical plugs should be used: existing ungrounded plugs should be changed immediately.

 

  • Electrical cords should be in good condition, out of travel paths, and free of any breaks in insulation. Extension cords are for temporary use only and must be disconnected at the end of every working period. Power strips with integrated overcurrent protection (breakers) are a preferred alternative. They should be UL approved, and cannot be ‘daisy-chained’ to increase length.

 

  • In the event of an electrical short, and only if it is safe to do so, unplug the appliance or trip the circuit breaker. The area in front of building electrical panels must be kept unobstructed.

 

  • Equipment and appliances that operate at higher currents (1,000 watts) must be plugged directly into the building's wall receptacles and never into a power strip. Some examples: Refrigerators, freezers, large centrifuges, sterilizers, vacuum pumps, water stills, hot plates, heat guns and microwaves.

 

  • Ovens- direct- heated ovens should only be used to dry glassware (and not flammables). Ovens that dry materials that off-gas noxious vapors should be contained in a hood or connected to the fume exhaust system.

 

  • Utility failure / Power Blips- Power blips are common during the summer thunderstorm season. Careful re-inspection of lab experiments and equipment should be conducted following a power blip or power failure. Verify that key systems, such as the HVAC, fume ventilation, and electrical circuits are still working properly.

 

  • An unintentional cross connection between the University water supply and wastewater may occur from a submerged inlet in your laboratory unless vacuum breakers are present on the faucet. "Draw down" occurs when city water pressure drops from low reservoir conditions, opening of fire hydrants, unbalanced demand on water circuits or from other causes. If your lab faucets have an attached Tygon or rubber hose to prevent splashing or to facilitate washing, it may siphon sink wastes and possibly raw sewage into the water lines. You must cut off each faucet hose at least 2 inches (5 cm) above the sink rim elevation. This gap will assure you that no back-siphonage of laboratory sewage will pollute our potable water supply.

 

  • Another common problem is that of "dry traps". A plumbing trap which has lost water seal through evaporation is likely to release sewer gases into your laboratory. Dry traps in adjacent rooms may also duct lab odors from remote labs into yours; this may account for unlocatable mystery odors that may be noticed. Pouring water or mineral oil into seldom used drains as needed will restore the water seal and assure you that no sewer gases will escape into your work environment. Floor drains as well as unused sinks are common sources. Consult with UVA Facilities Maintenance for recurring issues.