the hazards and state warnings. Take care when moving leaking cylinders of flammable gases so that accidental ignition does not occur. If feasible, move the leaking cylinder into a laboratory chemical hood until it is exhausted.

   Corrosive gases. Corrosive gases may increase the size of the leak as they are released, and some corrosives are also oxidants, flammable, or toxic. Move the cylinder to an isolated well-ventilated area, and, if possible, use suitable means to direct the gas into an appropriate chemical neutralizer. If there is apt to be a reaction with the neutralizer that could lead to a suck-back into the valve (e.g., aqueous acid into an ammonia tank), place a trap in the line before starting neutralization. Post signs that describe the hazards and state warnings.

   Toxic gases. The same procedure should be followed for toxic gases as for corrosive gases. Be sure to warn others of exposure risks. Move the cylinder to an isolated well-ventilated area. Direct the gas into an appropriate chemical neutralizer. Post signs that describe the hazards and state warnings.

Contact the supplier for specific information and guidance.

6.C.10.8 Handling Spills of Elemental Mercury

When spilled in a laboratory, mercury can become trapped beneath floor tiles, under cabinets, and even between walls. Even at very low levels, chronic mercury exposure can be a serious risk, especially in older laboratory facilities, where multiple historic spills may have occurred. Government and standard-setting organizations have established cleanup standards for laboratory spills. These stringent standards ensure the safety of trained laboratory personnel, students, and future occupants of the space.

A portable atomic absorption spectrophotometer with a sensitivity of at least 2 ng/m3 or other suitable instruments are used to find mercury residues and reservoirs that result from laboratory spills, and for the final clearance survey. Follow institutional procedures in cleaning up spills. General guidelines for handling incidental, non-emergency elemental mercury spills are as follows:

   First, isolate the spill area. Keep people from walking through and spreading the contamination.

   Wear protective gloves, booties, and a Tyvek® suit when necessary, while performing cleanup activities.

   Collect the droplets on wet toweling, which consolidates the small droplets to larger pieces, or with a piece of adhesive tape. Do not use sulfur; the practice is ineffective and the resulting waste creates a disposal problem.

   Consolidate large droplets by using a scraper or a piece of cardboard.

   Use commercial mercury spill cleanup sponges and spill control kits.

   Use specially designed mercury vacuum cleaners that have special collection traps and filters to prevent the emission of mercury vapors. A standard vacuum cleaner should never be used to pick up mercury.

   Waste mercury should be treated as a hazardous waste. Place it in a thick-walled high-density polyethylene bottle and transfer it to a central depository for reclamation.

   Decontaminate the exposed work surfaces and floors by using an appropriate decontamination kit.

   Verify decontamination to the current standards by using a portable atomic absorption spectrophotometer or other suitable instrument as described above.

Prevent mercury spills by using supplies and equipment that do not contain mercury. (For information about reducing the use of mercury in laboratories, see Chapter 5, section 5.B.8.)

6.C.10.9 Responding to Fires

Fires are one of the most common types of laboratory accidents. All personnel should be familiar with the general guidelines below to prevent and minimize injury and damage from fires. Hands-on experience with common types of extinguishers and the proper choice of extinguisher should be part of basic laboratory training. (See also Chapter 7, section 7.F.2.)

Be prepared to respond to a fire:

   Preparation is essential! Make sure all laboratory personnel know the locations of all fire extinguishers in the laboratory, what types of fires they can be used for, and how to operate them correctly. Also ensure that they know the location of the nearest fire-alarm pull station, telephone, emergency contact list, safety showers, and emergency blankets.

   In case of fire, immediately notify emergency response personnel by activating the nearest fire alarm. After initial containment, it is also important to report all fires to appropriate personnel for possible follow-up action.

   Even though a small fire that has just started can



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