(7) Additional Engineering Controls [24]
7.1 - Chemical Storage
Good housekeeping practice suggests that every chemical have an identifiable
storage place and if such is practical be returned there after use. A storage
scheme should be developed that ensures the segregation of incompatibles.
7.2 - General Guidelines for Storing Chemicals in Individual Laboratories
a. Because of the risk of placing incompatible materials side-by-side, a storage scheme based solely on alphabetizing is prohibited. An effort must be made to isolate particularly flammable, reactive, and/or toxic materials. Lists of incompatibles are available in various references. [25]
b. Storage areas should be checked periodically for cracked bottles, deteriorating labels, and other problems.
c. Storage trays are recommended to contain possible spills.
d. Chemicals should not be stored on the floor.
e. Chemical storage on benchtops should be kept to a practical minimum.
f. Chemical storage in hoods should be kept to a practical minimum for better airflow and more workspace. EPA requires secondary containment of chemicals stored in our hoods because they are fitted with drains; a chemical spill could potentially contaminate the groundwater.
g. Date labeling (discussed further in Section 10)i. Chemical containers should be labeled with the date when they are initially opened.
ii. At that time, it is recommended that a decision date be assigned and recorded on the label. On the decision date, an evaluation should be made as to whether to keep the chemical (assigning a new decision date) or to dispose of it. The practice of recording a decision date is particularly helpful in determining when certain tests, such as for peroxides, must be done.
iii. When provided, the manufacturer's expiration date should be displayed.h. Appropriate spill-control, cleanup, and emergency equipment must be available wherever chemicals are stored.
i. Refrigerators in which flammable materials are stored must be explosion-proof according to NFPA standards. Each refrigerator must have a sign with the information as to whether or not it may be used for storage of flammables.
j. In addition to the requirements for high-hazard materials (see Section 7.5), the following are in effect for security purposes:i. Chemicals stored in chaseways must be kept out of view. For this reason, glass-door cabinets and open shelving may not be used for chemical storage in chaseways.
ii. If not frequently used, large containers of even moderately dangerous chemicals should also be out of view.
7.3 - Storage of Flammables and Combustibles
Legal limits [26] on amounts of flammables and combustibles
will be observed for each laboratory space. As a rule of thumb, in any one lab
outside of an approved flammable storage cabinet, no more than 25 gallons of
flammable liquids with flashpoints below 22.8 C and boiling points below 37.8
C can be stored. Above these limits, up to 120 gallons of flammables can be
stored.
a. Storage in cabinets
i. Large containers of flammable materials must be stored in cabinets that meet OSHA and National Fire Protection Association specifications: Cabinet contents must be protected from temperatures exceeding 160 C for at least 10 minutes, enough time for personnel to evacuate the area.
ii. The cabinet doors must be kept closed other than at times of chemical transfer. Do not remove the air vent covers. Do not duct the cabinets to the ventilation system.
iii. No more than 60 gallons of flammables and 120 gallons of combustibles may be stored in one of these cabinets.b. Storage on the bench
i. Maximum container size: OSHA and NFPA limit the size of the container for classes of flammable and combustible materials. The more fire-resistant a container, the larger it may be. Only certified containers may be used.
ii. Safety cans: Portable and approved safety cans should be used when possible for storing flammable liquids. Flammable liquids in quantities greater than 1L should be stored in metal containers. Flammable liquids purchased in large containers should be repacked into smaller safety cans for distribution to laboratories. Cans greater than 5 gallons must be grounded and bonded during transfer of contents.
7.4 - Storage of Oxidizers and Corrosives: Guidelines are given in general references and in the University CHP.
a. High-hazard materials have special storage requirements with respect to security.
i. Radioactive materials and pathogens must be locked up and secured at all times.
ii. The following materials must be stored out of view: hazardous chemicals whose names would be popularly recognized, such as cyanide, strychnine, arsenic, etc.; large containers (kilogram quantities) of highly toxic or otherwise hazardous chemicals.b. Extremely toxic substances must be stored in unbreakable chemically resistant secondary containers.
c. Adequate ventilation must be provided in storage areas especially for toxics that have a high vapor pressure.
d. All dispensing of these materials must be conducted in a hood or glove box.
7.6 - Compressed Gases - Nonflammable, Flammable
a. Compressed gases must be stored away from direct or localized heat (including radiators, steam pipes, or boilers) in well-ventilated and dry areas and away from areas where they may be capsized (e.g. near elevators or doors to service corridors).
b. All compressed gases, including empty cylinders, must be secured in an upright position with chains, straps, or special stands of adequate strength; and must be capped when stored or moved. A maximum of three cylinders may be chained together in a nested, pyramid shape.
c. Empty cylinders should be separated from non-empty cylinders and labeled "empty."
d. A hand truck must be used for transporting gas cylinders to and from storage areas.
e. Cylinders of incompatible gases must be segregated by distance.
f. Cylinders of flammable gas should be segregated from other types.
7.7 - Glove Boxes
a. Glove boxes and glove bags are isolation units used for handling highly toxic chemicals and carcinogens. These are negative pressure units, so air leakage is into the unit. The ventilation rate must be at least two volume changes per hour and pressure at least 0.5 inch of water.
b. With a positive pressure unit, there exists the potential hazard of leakage into the laboratory.i. Positive pressure units are used when protection from atmospheric moisture or oxygen is required. Toxic chemicals should not be used in a positive pressure unit.
ii. These units must be regularly tested for leaks and must have a shutoff valve and pressure gauge installed.c. Exhaust air must be treated by scrubbing and/or absorption prior to release into the regular exhaust system.
7.8 - The Cold Room [27]
Temperature control rooms do not generally have fresh air ventilation. Do not
use highly volatile chemicals in the cold room. Also note that liquid nitrogen
stored in this room can displace oxygen and cause oxygen-deficient conditions.
7.9 - Emergency Equipment
At an orientation session for the individual PI's lab, all workers should be
made aware of the location of emergency equipment and first aid supplies. These
must be checked and maintained on a regular basis. Access must be free and clear.
a. Eye wash.
b. Shower - annual inspection arranged by the CHO.
c. Fire extinguishers - annual inspection arranged by the CHO.
d. Spill kit or absorbent material.
e. First aid kit.
7.10 - Miscellaneous
a. Trip hazards - Report loose floor tiles to the building manager for prompt repair. Do not extend cords or hoses across aisles. Do not allow empty bottles to accumulate in aisles.
b. Drains - Lab drain traps should be periodically filled with water so as to prevent toxic gases from entering the room via the building exhaust system.
c. The Chemistry Department maintains a shop vacuum for cleaning up floods. It is located in room 599A, next to the freight elevator, along with plastic tarps, pail and mop, and ladder.
7.11 - The Chemistry Department Stockroom
Stockroom access is limited to specified personnel. General design and operation
of stockrooms are discussed in the University CHP [28].
The stockroom can supply most of the safety items mentioned in this CHP. It can also supply a limited number of chemicals. Be sure to use a bottle carrier for secondary containment when you transport reactive chemicals (e.g. strong acids or bases, flammables) from the stockroom.
References:
[24] Except as otherwise noted, section 7 is adapted from the Stony Brook University CHP pp 40-42.
[25] See for example Safety in Academic Chemistry Laboratories, 1995 edition, pp 73-75.
[26] OSHA Regulations (Standards-29 CFR) Flammable and Combustible Liquids. - 1910.106 <http://www.osha-slc.gov/OshStd_data/1910_0106.html> accessed November 00.
[27] From the University of Vermont CHP.
[28] Stony Brook University CHP pp 42-44. This reference
is for informational purposes only. Many of its provisions are not applicable
to the Chemistry Department stockroom.