A. Access Control

The Principal Investigator must control access to laboratories that contain chemicals. Keep the laboratory door closed while experiments are in progress. This practice not only protects persons who might otherwise enter the laboratory, it reduces interruptions to laboratory staff that could lead to accidents. Laboratory hoods work best, and offer the most worker protection, when the doors to the laboratory are closed.

B. Personal Practices

Wash your hands immediately after completion of any procedure involving chemicals, and when leaving the laboratory. Soap must be either liquid or foam in a pump dispenser. Do not use bar soap in laboratories. Do not use liquid soap bottles that you must invert and squeeze. Soap dispensers can be wall-mounted type or freestanding countertop bottles.

Figure 6.1
Wall-mounted and freestanding liquid and foam soap pump dispensers are appropriate for laboratory use. Invert-squeeze soap bottles and bar soaps are not acceptable for laboratory use.

In laboratories where toxic materials are used, do not eat, drink, smoke, chew gum, apply cosmetics, or store utensils, food, and food containers, unless your laboratory has an authorized and clearly marked food item area. Refer to the food policy in Chapter 3. In some laboratories, it might not be possible to establish a food item area due to the lack of adequate containment of volatile or toxic substances. If your laboratory has a food item area, make sure no chemicals, procedures, or laboratory equipment end up in the area. Remove gloves or other personal protective equipment that could introduce contamination to the food item area. Consider posting a reminder or labeling equipment.

Figure 6.2
Improper use of food item areas. Do not handle chemicals, or wear contaminated gloves, in a food item area. Do not place laboratory equipment (such as this water bath) within three feet of a designated food item area.

Use mechanical pipetting aids for all pipetting procedures. NEVER MOUTH PIPETTE.

C. Decontamination of Work Surfaces

Protect work surfaces from contamination by using “bench paper” (disposable plastic-backed absorbent paper) or stainless steel trays. Place the plastic side down and the absorbent side facing up. Change worn or contaminated bench paper and dispose properly. Decontaminate other items and equipment with appropriate solvents when contaminated during experiments.

D. Minimizing Aerosols

Since a procedure with an open vessel of liquids or powders generates aerosols, you should develop techniques that will minimize the creation of aerosols. Such techniques might include discharging liquids from pipettes as close as possible to the fluid level of the receiving vessel, or allowing the contents to run down the wall of the receiving vessel. Dropping the contents from a height generates more aerosols.

Also, avoid rapid mixing of liquids with pipettes by alternate suction and expulsion, or forcibly expelling material from a pipette. Take extra care when discarding contaminated gloves or plastic-backed absorbent paper used to cover the work surface, to avoid aerosolizing contaminants. Clean floors with a wet mop or with a vacuum cleaner equipped with a HEPA filter, as dry sweeping or dry mopping contaminated laboratory floors could aerosolize contamination.

E. Use of Laboratory Hoods and Biological Safety Cabinets

When used properly, laboratory hoods and biological safety cabinets are among the most effective means for controlling exposures to toxic chemicals, since they move substances away from you before they can reach your breathing zone. Refer to Chapter 16: Biological Safety Cabinets and Chapter 17: Laboratory Hoods for a full discussion of the uses and limitations of these very important engineering controls.