Work Practices

Signs and Labels

The entrance to all laboratories working with recombinant and/or biohazardous material must be posted by Research Laboratory and Safety Services.

All tools and equipment that are used with recombinant and/or biohazardous material must be labeled as biohazardous. This includes, but is not limited to: centrifuges, refrigerators, freezers, incubators, growth chambers, storage cabinets, liquid nitrogen Dewars, and transport containers.

Sharps Precautions Requirements

The University of Arizona requirements for the safe handling of sharps, including needles, scalpels, broken glassware, and sharp-like objects including pipette tips, must be adhered to, in order to reduce the risk of sharps injuries.  Precautions, including those listed below, must always be taken with sharp items.

These include:

  • Needles must not be bent, sheared, broken, recapped, removed from disposable syringes, or otherwise manipulated by hand before disposal.
  • Used, disposable needles and syringes must be carefully placed in conveniently located, puncture proof containers used for sharps disposal.
  • Non-disposable sharps must be placed in a hard walled container for transport to a processing area for decontamination, preferably by autoclaving.
  • Broken glassware must not be handled directly. Instead, it must be removed using a brush and dustpan, tongs, or forceps and disposed in leak-proof, puncture proof containers. Plastic ware should be substituted for glassware whenever possible.

Sharp-like objects, including plastic pipette tips of 1 mL volume or less, contaminated with biohazardous and/or recombinant nucleic acid material, must be placed in a container that is puncture resistant prior to placing in a red bag for disposal. Acceptable puncture resistant containers include used plastic bottles with a loose seal (1/4 turn from being fully tightened) and bag-lined cardboard boxes.

Protecting Vacuum Systems

The aspiration of tissue culture media from cultures and supernatants from centrifuged samples into primary collection flasks is a common laboratory procedure. Protection against pulling biological aerosols or overflow fluid into the vacuum system is necessary.

  • An overflow flask and a cartridge type filter are required to provide protection for the vacuum line.
  • For assembling the apparatus, flexible tubing is used of appropriate inside diameter for the flask and filter fittings and of sufficient wall thickness for the applied vacuum. Filter flask of capacities from 250 to 4,000 ml may be used for the overflow flask depending on the amount of fluid that could be aspirated out of the collection flask.
  • The overflow flask contains a disinfectant solution appropriate for the recombinant and/or biological material in use. Bubbling of air through the disinfectant can cause foam which can shut off the vacuum if it reaches the filter.
  • Change the filter if it becomes contaminated.


Pipetting is the act of transferring, measuring or dispensing a liquid through an apparatus typically consisting of a narrow tube.  Pipets can be constructed of a variety of glass or plastic materials. Liquids are drawn into the pipet using hand-held bulbs, manual pipet aids, motorized pipet aids, or various other vacuum sources. Pipetting is a routine function in most laboratories; therefore the safety concerns must not be overlooked.

The following safety rules must be followed when using pipets:

  • Never pipet by mouth.
  • Visually inspect the pipet prior to inserting it into any pipet aid. Make sure the pipet does not have any cracks.
  • Always dispose of pipets in hard walled, leak proof containers.
  • Routinely clean and inspect pipet aids and bulbs. Damaged pipet aids and weakened bulbs must be discarded.
  • Motorized pipet aids should have some type of filter (typically 0.45 μm or 0.22 μm) to prevent liquid from accidentally being drawn into the housing.

Storage of Biological Materials

  • A biological hazard sign must be clearly posted on storage areas such as refrigerators, freezers, cabinets, etc. containing recombinant and/or biohazardous materials.
  • All containers and/or racks are to be clearly labeled to identify the contents.
  • Storage containers must be intact (no tears or cracks), leak-proof and covered or closed to avoid spills or contamination. Secondary containment must be used when possible.
  • All materials should be inventoried and organized.
  • Any substance being stored in a freezer must be placed in a labeled container designed for low temperature storage.
  • If flammable materials are used, they must be stored in equipment that is designed for this purpose.
  • No personal items must be stored in lab refrigerators, freezers or incubators (e.g. food, beverages).
  • When storage equipment needs repair, calibration or transport, it must be completely decontaminated prior to starting work or being removed.


Each Approval Holder is responsible for performing a physical inventory of their long term storage (i.e., freezers and liquid nitrogen tanks) annually. This annual physical inventory must be documented using the Annual Physical Inventory Check Form and the records kept available for inspection.

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