Criteria for
Implementation of Chemical
Control Measures
Engineering controls, personal protective equipment, hygiene practices,
and administrative controls each play a role in a comprehensive
laboratory safety program. Implementation of specific measures must be
carried out on a case-by-case basis, using the following criteria for
guidance in making decisions. Assistance is available from the
Department of Environmental Health and Safety.
- Engineering
Controls
- Personal
Protective Equipment
- Hygiene
Practices
- Administrative
Controls
1. Engineering
Controls
a) Fume Hoods
The laboratory fume hood is the major protective device available to
laboratory workers. It is designed to capture chemicals that escape
from their containers or apparatus during experimentation and remove
them from the
laboratory environment before they can be inhaled. Characteristics to
be considered in requiring fume hood use are physical state,
volatility, toxicity, flammability, eye and skin irritation, odor, and
the potential for producing aerosols. A fume hood should be used if a
proposed chemical procedure exhibits any one of these characteristics
to a degree that (1) airborne concentrations might approach the action
level (or permissible exposure limit), (2) flammable vapors might
approach one tenth of the lower explosion limit, (3) materials of
unknown toxicity are used or generated, or (4) the odor produced is
annoying to laboratory occupants or adjacent units.
Procedures that can generally be carried out safely outside the fume
hood include those involving (1) water-based solutions of salts, dilute
acids, bases, or other reagents, (2) very low volatility liquids or
solids, (3) closed systems that do not allow significant escape to the
laboratory environment, and (4) extremely small quantities of otherwise
problematic chemicals. The procedure itself must be evaluated for its
potential to increase volatility or produce aerosols.
In specialized cases, fume hoods will contain exhaust treatment
devices, such as water wash-down for perchloric acid use, or charcoal
or HEPA filters for removal of particularly toxic or radioactive
materials.
b) Safety Shields
Safety shields, such as the sliding sash of a fume hood, are
appropriate when working with highly concentrated acids, bases,
oxidizers or reducing agents, all of which have the potential for
causing sudden spattering or even explosive release of material.
Reactions carried out at non-ambient pressures (vacuum or high
pressure) also require safety shields, as do reactions that are carried
out for the first time or are significantly scaled up from normal
operating conditions.
c) Biological Safety Cabinets
Biological Safety Cabinets (BSC), also known as tissue culture hoods or
laminar flow hoods, are the primary means of containment for working
safely with infectious microorganisms. Cabinets are available that
either exhaust to the outside or that recirculates HEPA filtered air to
the laboratory. They are not to be used for working with volatile or
hazardous chemicals unless they are specifically designed for that
purpose and are properly vented. Generally, the only chemical work that
should be done in a BSC is that which could be done safely on a bench
top involving chemicals that will not damage the BSC or the HEPA
filter. For proper cabinet selection and use see, the CDC publication Primary
Containment for Biohazards.
d) Other Containment Devices
Other containment devices, such as glove boxes or vented gas cabinets,
may be required when it is necessary to provide an inert atmosphere for
the chemical procedure taking place, when capture of any chemical
emission is desirable, or when the standard laboratory fume hood does
not provide adequate assurance that overexposure to a hazardous
chemical will not occur. The presence of biological or
radioactive materials may also mandate certain special containment
devices. High strength barriers coupled with remote handling
devices may be necessary for safe use of extremely shock sensitive or
reactive chemicals.
Highly localized exhaust ventilation, such as is usually installed over
atomic absorption units, may be required for instrumentation that
exhausts toxic or irritating materials to the laboratory environment.
Ventilated chemical storage cabinets or rooms should be used when the
chemicals in storage may generate toxic, flammable or irritating levels
of airborne contamination.
2. Personal
Protective Equipment
a) Skin Protection
As skin must be protected from hazardous liquids, gases and vapors,
proper basic attire is essential in the laboratory. Long hair
should be pulled back and secured and loose clothing (sleeves, bulky
pants or skirts) avoided to prevent accidental contact with chemicals
or open flames. However, bare feet, sandals and open-toed or perforated
shoes are not permitted in any laboratory. Short pants and short skirts
are not permitted unless covered by a lab coat. Long pants should
be worn to cover skin that could be exposed during a spill.
Lab coats are strongly encouraged as routine equipment for all
laboratory workers. It is the responsibility of the employer to
purchase and wash lab coats for employees who request them or are
required to wear them. Lab coats are required when working with
radioactive materials, biologically-derived toxins, Biosafety Level II
organisms, carcinogens, reproductive toxins, substances which have a
high degree of acute toxicity, and any substance on the OSHA PEL list
carrying a "skin" notation. See Appendix B for chemical listings.
Lab coats cannot be assumed to provide complete protection against all
agents, but will provide an extra layer that can be removed if
accidentally contaminated, buying time for the researcher to get to the
emergency shower and minimize direct skin contact. For strong acids and
bases, a lab apron impervious to liquids would be a more appropriate
choice.
Gloves made of appropriate material are required to protect the hands
and arms from thermal burns, cuts, or chemical exposure that may result
in absorption through the skin or reaction on the surface of the skin.
Gloves are also required when working with particularly hazardous
substances where possible transfer from hand to mouth must be avoided.
Thus gloves are required for work involving pure or concentrated
solutions of select carcinogens, reproductive toxins, substances which
have a high degree of acute toxicity, strong acids and bases, and any
substance on the OSHA PEL list carrying a "skin" notation.
Since no single glove material is impermeable to all chemicals, gloves
should be carefully selected using guides from the manufacturers.
General selection criteria are outlined in Prudent Practices, p. 132,
and glove selection guides are available on the web.
However, glove-resistance to various chemicals materials will vary with
the manufacturer, model and thickness. Therefore, review a
glove-resistance chart from the manufacturer you intend to buy from
before purchasing gloves. When guidance on glove selection for a
particular chemical is lacking, double glove using two different
materials, or purchase a multilayered laminated glove such as a
Silvershield or a 4H.
b) Eye Protection
Eye protection is required for all personnel and any visitors whose
eyes may be exposed to chemical or physical hazards. Side shields on
safety spectacles provide some protection against flying particles, but
goggles or face shields are necessary when there is a greater than
average danger of eye contact with liquids. A higher than average risk
exists when working with highly reactive chemicals, concentrated
corrosives, or with vacuum or pressurized glassware systems. Contact
lenses may be worn under safety glasses, goggles or other eye and face
protection. Experts currently believe the benefits of consistent use of
eye protection outweigh potential risks of contact lenses interfering
with eye flushing in case of emergency.
c) Respiratory Protection
Respiratory protection is generally not necessary in the laboratory
setting and must not be used as a substitute for adequate engineering
controls. Availability of respiratory protection for emergency
situations may be required when working with chemicals that are highly
toxic and highly volatile or gaseous. If an experimental protocol
requires exposure above the action level (or PEL) that cannot be
reduced, respiratory protection will be required. Rarely, an
experimental situation may potentially involve IDLH (immediately
dangerous to life or health) concentrations of chemicals, which will
require use of respiratory protection. All use of respiratory
protective equipment is covered under the UMD
Respiratory Protection Program.
3. Hygiene Practices
Eating, drinking and chewing gum are all strictly prohibited in any
laboratory with chemical, biological or radioactive materials.
Researchers must also restrict other actions (such as
applying lip balm or rubbing eyes) which could inadvertently cause
exposure to research materials. Consuming alcohol or taking
illegal drugs in a research laboratory are strictly prohibited, as such
actions potentially endanger the health and safety of not only the
user, but everyone in the building. Infractions will be met with
serious disciplinary action.
Before leaving the laboratory, remove personal protective
equipment/clothing (lab coat and gloves) and wash hands
thoroughly. Do NOT wear laboratory gloves, lab coats or scrubs in
public spaces such as hallways, elevators or cafeterias.
4. Administrative Controls
Supervisors shall consider the hazards involved in their research, and
in written research protocols, detail areas, activities, and tasks that
require specific types of personal protective equipment as described
above. Researchers are strongly encouraged to prioritize research
so that work with hazardous chemical, biological or physical agents
occurs only during working hours (8 am – 5 pm, Monday through
Friday). After-hours (on nights and weekends) work should be
restricted to nonhazardous activities such as data analysis and report
writing. If hazardous materials must be used at nights or on
weekends, ensure that at least one other person is within sight and
ear-shot to provide help in an emergency. Undergraduate workers
are prohibited from working alone in the laboratory unless there is a
review and formal approval by the department’s RSO and/or safety
committee.
Research Safety Officers must coordinate and/or conduct inspections of
laboratories in their area of responsibility and ensure laboratory
supervisors address any noted deficiencies. An audit checklist is
available in Appendix G. RSOs can report cases of continued
non-compliance to the unit head and to the UMD Environmental
Health and Safety Office (EHSO). The RSO, in conjunction with EHSO and
the
unit head, has the authority to halt research activities that present
an imminent hazard. |
