F&M CHEMICAL HYGIENE PLAN
4. CHEMICAL HYGIENE AND SAFETY
4.3 Hazard Class-Specific Safety Procedures
Written Standard Operating Procedures. All routine laboratory procedures should refer to the applicable precautions described in this section. Laboratory notebook records of non-routine procedures should cite hazard information regarding the materials used and reference the applicable precautions described in this section. Laboratory workers are required to read and understand those practices before commencing with a procedure.
4.3.1 Procedures for Toxic Chemicals (see Section 5.2.1 for definition)
The overall objective of procedures for handling toxic materials is to minimize exposure of the laboratory worker by taking all reasonable precautions. This may be achieved by the use of the following :
- Protect hands and forearms by wearing either gloves and a laboratory coat or suitable long gloves to avoid contact of the toxic material with the skin.
- Perform all procedures involving the toxic materials in an operating fume hood or other suitable containment device.
- Immediately after working with a toxic material wash hands and arms.
4.3.2 Procedures for Fire Hazard Chemicals (see Section 5.2.2 for definition)
For a fire to occur, three distinct conditions must exist simultaneously: a concentration of flammable gas or vapor that is within the flammable limits of the material; an oxidizing atmosphere, usually air; and a source of ignition. Removal of any of these three will prevent the start of a fire.
Basic precautions for the safe handling of fire hazard chemicals include:
- Fire hazard chemicals should be handled only in areas free from sources of ignition.
- Fire hazard chemicals should never be heated by using an open flame. Preferred heat sources include steam baths, water baths, oil baths, and hot air baths and to a lesser extent heating mantles and electric hot plates.
- When transferring fire hazard liquids from or to metal equipment, static generated sparks should be avoided by connecting the containers either directly or indirectly through a common ground, and by using grounding straps.
- Ventilation is one of the most effective ways to prevent the formation of fire hazard mixtures. An exhaust hood should be used whenever 100 mL or more of a fire hazard chemical is used.
- Fire hazard chemicals should be stored in a flammable solvent storage area or flammable storage cabinets. The NFPA specifies safe storage containers according to Table 5.1 on page 5-3.
If you discover fire or smoke:
- Warn others to evacuate the area. Pull the nearest fire alarm and exit quickly. Do not use elevators to evacuate the building: use the stairs.
- Do NOT attempt to extinguish a fire unless you have first warned others and/or activated the alarm.
- Go to a safe place and call Public Safety (x3939) to report all pertinent information.
A fire contained in a small vessel can usually be suffocated by covering the vessel. If the fire is burning over an area too large to be suffocated quickly (within 30 to 45 seconds) and simply, leave the fire-fighting to those who have been trained and equipped. If you have been trained in the use of a fire extinguisher, fight the fire from a position from which you can escape, and only if you are confident that you will be successful. It is easy to underestimate a fire. Do not expose yourself to unwarranted risk.
There are four classes of fires which may occur in a laboratory:
Class A - fires in ordinary combustible materials, such as wood, cloth, paper, rubber and some plastics;
Class B - fires in flammable liquids, oils, greases and flammable gases;
Class C - fires involving energized electrical equipment; and
Class D - fires in combustible metals such as magnesium, titanium, zirconium, sodium, lithium and potassium.
The specific type of extinguisher should be selected with consideration for the hazards to be protected. Water is a suitable extinguishant only for Class A fires. The carbon dioxide extinguishers available in most laboratories on campus are to be used only for Class B and C fires. Only extinguishing agents approved for use on the specific combustible metal hazard, e.g., G-1� powder for magnesium fires or Lith-X for lithium fires, should be used for Class D fires. The extinguishers should be located conspicuously where they will be readily accessible in the event of a fire, such as along normal paths of travel including exits, and preferably close to any known hazard.
4.3.3 Procedures for Reactive Chemicals (see Section 5.2.3 for definition)
The hazard associated with materials classified as reactive is not the total energy released, which is a constant determined by the thermochemistry of the system and the amount of materials present, but rather with the variable and potentially high rate at which that energy may be released. Factors which affect reaction rates include the following:
- Proportions or concentrations of the reactants.
- Purity of materials, presence of catalytic impurities.
- Degree of agitation and mixing.
- Viscosity of reaction mix, as influenced by diluents or solvents.
- Other experimental variables, e.g., rates of addition, reactor atmosphere, pressure, etc.
Control of these factors can be provided by the following procedures:
- Quantities should be limited in initial experiments to assess the level of energy release and potential control problems; no more than 0.25 grams of product and no more than 1 gram of reactants. Special reviews should be established to examine operational and safety problems involved in scaling up.
[One gram of TNT exploding can produce sufficient pressure to rupture the eardrum at a distance of 2.5 feet for 1% of the population. At a distance of 1 foot 50% of the population suffer ruptured eardrums. (NFPA 45-30, Fire Protection for Laboratories Using Chemicals, 1982.)]
- Barriers should be used to protect personnel and equipment from injury or damage. The barriers should completely encircle the reaction vessel.
- Tongs should be used for handling containers of the hazardous material at a safe distance. Remote-controls, such as stopcock turners, labjack turners and remote cable controllers, should be available to avoid exposure of any part of the body to injury.
- Gloves, such as yellow "electrical" linesman's gloves, should be worn whenever it is unavoidably necessary to reach behind a shielded area while an experiment is in progress.
- A face shield, providing throat protection, should be worn at all times whenever the worker is in an exposed position, such as when bench shields are moved aside, when handling or transporting materials, or when manipulating equipment.
- Laboratory coats, made of slow burning material and fitted with snap buttons, should be worn at all times to reduce minor injuries from flying glass or an explosive flash.
4.3.4 Procedures for Corrosive Chemicals (see Section 5.2.4 for definition)
Corrosive chemicals erode the skin and are particularly damaging to the eyes. Inhalation of vapors or mists of these substances can cause severe bronchial irritation and damage the respiratory epithelium. Many of the general recommendations for safe practices in the laboratory are especially applicable to the handling of corrosive substances. Particular attention should be given to the use of protective apparel, including wearing both safety goggles and face shield as well as gloves known to be resistant to permeation or penetration, and a laboratory apron or laboratory coat.