Fume hoods capture, contain, and expel emissions generated by hazardous chemicals. Generally, it is a good idea to conduct all chemical experiments in a fume hood. While you may be able to predict the release of undesirable or hazardous effluents, in some operations surprises can always happen. Therefore, the fume hood offers an extra measure of protection.

Before use, check to see that your hood has an inspection tag. This will tell you the date of the most recent hood evaluation.

Some laboratory procedures may require the use of perchloric acid. The use of this material may cause the formation of explosive perchlorate crystals. Special fume hoods, commonly known as Perchloric Acid Fume Hoods, MUST be used for this purpose. These hoods have self-contained wash-down units to inhibit crystal formation.

The purpose of a fume hood is to prevent the escape of contaminants into the laboratory. This is done by drawing air from the laboratory, past the operator, into the hood. The concentration of the contaminant in the actual breathing zone of the operator must be kept as low as possible. The efficiency of the hood to provide adequate protection is dependent upon the following prime concerns:

1. The Control Velocity at the Hood Face

• Face velocities of 80-100 fpm (feet per minute) will provide adequate containment of laboratory contaminants, if the overall installation can be rated as "good" in the reference to the other listed performance factors (see 2 and 3 below). Control velocities must overcome the particle kinetics of aerosols, the molecular diffusion of gases and vapors, and all other "normal" activities which take place inside and outside of the hood. The vector of the air at the face of the hood must be inward and perpendicular to the face. Flows lower than 80 fpm do not provide the safety factors desired for normal conditions such as operator movements. Flows higher than 100 fpm are not required for "good" laboratory arrangements and do not improve performance for poor arrangements.

2. Air Movement and Flow Patterns in the Room

• The effect of air movement within the laboratory on the performance of hoods is directly related to hood location and the influence of air supply systems. Hood locations must be away from doors, windows, and pedestrian traffic. Air from these sources can have velocities several orders of magnitude greater than the hood face velocity, creating the potential for dragout or displacement of contaminated air from the hood. Air from outlets such as ceiling and/or wall diffusers, must either be controlled to assist in the performance of the hood or directed so that the energy is lost before entering the zone of influence. Air from the makeup systems should not exceed 20-25 fpm in the hood face area (measured with the hood exhaust "off"). If these criteria are judged satisfactory, the system then can be considered "good" and the required face velocities of 80-100 fpm are valid.

3. The Effect of the Operator on the Air Flow Pattern at the Hood Face

• The turbulent air patterns resulting from the passage of makeup air around an operator standing in front of a hood, have tremendous effects on the air flow characteristics. Serious losses of contaminants from the hood can occur unless the low pressure area in front of the operator is minimized via the proper use of makeup air and the assurance of sufficient capture velocity at the face of the hood.

4. Turbulence Within the Hood

• As air enters the hood, it is drawn past equipment and sources of contamination toward the exhaust slots. At an airflow greater than needed to provide a good vector and containment, excessive turbulence can cause a "rolling effect" in the hood chamber. This increases the potential for greater mixing of contaminated air and room air at the face of the hood. Under poor laboratory hood arrangements, greater turbulence can result in excessive spill-out of contaminated air into the room. For this reason, it is obvious that substandard hood operations cannot be upgraded merely by increasing air flow.

5. Recommended Work Practices

• All laboratory workers with access to a laboratory chemical fume hood should be familiar with its use.
• Always work at least six inches back into the hood (six inches beyond the sash line) keeping the sash line between your body and your work.
• Set the adjustable baffles on the back wall of the hood so that the one on top is about 3/4 of an inch from the ceiling of the hood compartment, and the lower baffle is fully open. This setting will provide the most uniform flow distribution through the hood face for most laboratory operations. A notable exception is the performance of experiments resulting in the discharge of effluents with high thermal buoyancy.
• Don't use laboratory chemical fume hoods as chemical storage casework -- keep the work surfaces clean and uncluttered.
• Beware of situations when the hood requires sash position mark to denote a minimally acceptable face velocity. This practice is often necessary because the hood cannot deliver the required velocity in the fully open position. However, any time the sash mark must be posted lower than 18 inches up from the hood work surface, there are probably basic (and possibly critical) deficiencies that should be investigated and rectified.

6. Maintenance

• Fume hoods should be surveyed on a regular basis.
• The hood should always be in good condition and capable of routine use. Any hood or component of ventilation not properly functioning must be taken out of service and clearly tagged.
• The lab worker should not be able to detect strong odors released from materials in the hood area. If odors are detected, check to make sure that the ventilation fan is turned on.
• An emergency plan should exist in case of hood ventilation malfunction.
• All protective clothing should be worn when working with chemicals in the hood. In addition to gloves, safety glasses, and lab coats, a face shield will provide an extra measure of safety from reactive chemicals.
• Solid objects or materials should not be allowed to enter the exhaust ducts at the rear of the hood, as they can become lodged in the duct or fan.

B. Chemical Storage Cabinets, Storage Laboratory Casework.

Storage of flammables and corrosives in the lab should be limited to as small a quantity as possible. They should be stored in ventilated casework which meet OSHA 1910.106d and NFPA 30 specifications.

1. Use and Maintenance

• Chemicals should NEVER be stored in alphabetical order (unless already separated out into compatible groups). This system may contribute to the high probability of incompatible materials being stored next to one another.
• Incompatible reagents should not be stored next to each other.
• Storage outside the casework should be kept to a minimum.
• The vent cap on chemical storage casework should not be removed from its location unless the casework attached to an existing ventilation system.
• Glass containers should be stored on the bottom shelf of storage casework, if possible.

2. Types of Casework

• Flammable liquid cabinets -- are designed for storage of flammable or combustible liquids.
• Acid/corrosive cabinets -- are designed for corrosion resistance.
• Bulk storage cabinets -- can be used for storage of flammable and corrosive liquids outside the laboratory setting.

C. Individual Storage Containers

Selecting the best means of storage for chemical reagents will, to a great extent, depend on that reagent's compatibility with the container.

A safety can is an approved container of no more than five gallons (19 liters) capacity. It has a spring-closing lid and spout cover, and is designed to safely relieve pressure buildup within the container.

Vent caps may be purchased for original manufacturer's glass containers to help minimize explosion hazards.

D. Refrigerators

While domestic refrigeration units are appropriate for keeping foods cold, they are not designed to meet the special hazards presented by flammable materials. Therefore, laboratory refrigerators should be carefully selected for specific chemical storage needs.

To prevent potential safety hazards, the length of storage of any material should be kept to a minimum. In addition, refrigerators should be periodically inspected.

1. Use and Maintenance

• Each refrigerator, freezer, or cooler should be prominently labeled with appropriate hazard signs to indicate whether it is suitable for storing hazardous chemicals. To be on the safe side, label chemical hazard refrigerators with the sign "For Chemical Storage Only. No Food or Drink Allowed."
• If radioactive materials are to be stored, a refrigerator must be clearly labeled "Caution, Radioactive Material. No Food or Beverages may be stored in this unit."
• The containers placed in the refrigerator should be completely sealed or capped, securely placed, and permanently labeled. Avoid capping materials with aluminum foil, corks, and glass stoppers.
• Refrigerators should be frost free to prevent water drainage.

2. Types of Refrigerators

• Because ignitable vapors can build up in refrigerators, it is important to store materials in specially-designed units. These refrigerators will have self-contained electrical elements to avoid spark-induced explosions.
• Explosion-proof refrigerators are specifically designed for hazardous environments, featuring enclosed motors to eliminate sparking.

E. Eye Wash Stations

Eye wash stations provide an effective means of treatment when chemicals come in contact with the eyes. Eye wash stations should be readily available and accessible to all laboratory personnel.

The facility should be clearly marked and in accessible locations no more than 10 seconds or 50 feet away from every lab work station. Laboratory workers should be able to locate the nearest eye wash facility with their eyes closed (eye injuries may involve temporary blindness).

Eye injury usually accompanies a skin injury. For this reason, eye wash stations should be located near the safety shower so that eyes and body can be washed.

1. Use and Maintenance

• Eyelids have to be forcibly opened to ensure effective washing behind the eyelid.
• Be sure to wash from the nose out to the ear this will avoid washing chemicals back into the eye or into an unaffected eye.
• Flood eyes and eyelids with water/eye solution for a minimum of 15 minutes.
• Remove contact lenses as soon as possible to rinse eyes of any harmful chemicals.
• Cover both of the victim's eyes with a clean or sterile gauze.
• Plumbed epuipment shall be activated weekly to verify proper operation.
• Eye wash stations should be inspected annually to assure conformance with ANSI Z358.1 section 5 requirements.
• Plumbed eye wash stations should have protective covers to protect nozzles from airborne contaminants.

2. Types of Eye Wash Stations

• Gravity Feed Self-Contained -- provides the laboratory worker with emergency eye wash treatment in areas inaccessible to plumbing.
• Faucet-Mounted -- (pin or push plate activators) provides continuous water flow while freeing hands to open eyelids. It turns a standard faucet into a practical emergency eye wash station.
• Laboratory Bench -- sprays with a squeeze handle can be installed through the bench top for instant availability.
• Swivel Eye Wash -- mounts on lab bench or counter top adjacent to a sink. It swivels 90 degrees over the sink for use, or out of the way for storage.

F. Safety Showers

Safety showers provide an effective means of treatment in the event that chemicals are spilled or splashed onto the skin or clothing. Safety shower facilities should be installed wherever chemicals are present (e.g. acids, alkalis, or other corrosive materials) and must be readily available to all personnel.

1. Use and Maintenance

• Safety showers should be in a clearly marked and accessible location. The facility should be no more than 50 feet, or 10 seconds, away from every lab workbench.
• Laboratory workers should be able to locate the shower(s) with their eyes closed (emergency situations may leave victim temporarily blind).
• Safety showers are operated by grasping a ring chain or triangular rod.
• The pull mechanism is designed for people of all heights. It should always be accessible and hang freely.
• Safety shower should supply a continuous stream of water to cover the entire body.
• Individuals should remove clothing, including shoes and jewelry, while under an operating shower.
• Safety showers should be located AWAY from electrical panels or outlets.
• Plumbed epuipment shall be activated weekly to verify proper operation.
• Safety showers should be inspected annually to assure conformance with ANSI Z358.1 section 5 requirements.
• If at all possible, safety shower facilities should be installed near appropriate drainage systems.

2. Types of Safety Showers

• Ceiling/Wall Emergency Shower -- provides a continuous water flow and mounts directly to overhead vertical pipes or horizontal wall pipes.
• Deck-Mounted Drench Hose -- is hand operated for quick spot washing of injuries.
• Floor-Mounted Emergency Combination -- eye wash/face and body wash mounts directly to horizontal wall pipes.

G. Fire Safety Equipment

1. Alarms

• Alarms are designed so that all endangered laboratory personnel are alerted. All faculty, staff and students should become familiar with the EXACT LOCATION of the fire alarm stations nearest to their laboratory.

2. Extinguishers

• Extinguishers are classified according to a particular fire type and are given the same letter and symbol classification as that of the fire.

• TYPE A -- Combustibles wood, cloth, paper, rubber and plastics
• TYPE B -- Flammable Liquids oil, grease and paint thinners
• TYPE C -- Energized Electrical Equipment electrophoresis
• TYPE D -- Combustible Metals (magnesium, titanium, sodium, lithium, potassium)

• Multipurpose Extinguishers are highly recommended because they are an effective agent against Types A, B, and C fires.
• Extinguishers should be identified by appropriate signage and securely located on the wall near an exit. All extinguishers should be inspected at least every 12 months for broken seals, damage, low gauge pressure, or improper mounting. Units should be replaced or recharged if they have been used, damaged, or discharged.

How To Use A Fire Extinguisher

Fire extinguishers are not designed or intended to extinguish large fires, but if used properly, can control or extinguish a small fire. A small fire is defined as one that could occur in a standard office trash can. When a fire or suspected fire, i.e., smoke, is discovered, the first reaction should always be to activate the fire alarm system, call 911, and evacuate the building according to the evacuation plan. Fire extinguishers are required to be posted in all publicly occupied buildings and can be used provided the person is properly trained. The following are guidelines in making the decision as whether to use the unit, and how to use the extinguisher.

HOW/SHOULD I USE THE EXTINGUISHER??? If you have to ask yourself this, then the answer is NO. In an emergency don't use the unit, pull a fire alarm or contact your security office and leave the building according to the evacuation instructions posted. Improper use of a  fire extinguisher may lead to serious injury and accelerate the spread of fire due to splattering, electrical conductivity etc... Contact your Safety Officer and inquire about receiving appropriate training.

HOW TO USE AN EXTINGUISHER: "PASS"

1. PULL THE PIN: Place your hand on the top of the cylinder and pull the pin. This will unlock the handle and allow you to activate the unit.
2. AIM: Point the nozzle of the hose at the base of the fire.
3. SQUEEZE: the handle (lever) releasing the fire fighting agent.
4. SWEEP: the nozzle from side to side over the fire. Keep the nozzle/hose directed at the base of the flame. Empty the fire extinguisher onto the fire.

PERSONAL SAFETY PRECAUTIONS:

• Never reach over the fire.
• Never allow the fire to get between you and the exit from the room.
• Never enter an unknown area to fight a fire, especially in a chemistry lab.
• Always notify the proper fire officials.

3. Blankets

• Laboratory personnel are DISCOURAGED from using fire safety blankets as a means to extinguish a fire.
• Fire safety blankets should be used as a means to keep shock victims warm.

4. Sand/Absorbent Material

• Designed for fast and easy extinguishing of small fires in the laboratory.
• These materials should be stored in a handy dispenser, appropriately labeled, and used according to the type of fire.
• Do not use sand buckets as ash trays!

5. Sprinklers

• Sprinklers are automatically activated. Laboratory workers should not attempt to shut off the system.
• Items in the lab should be stored at least 18 inches away from the sprinkler heads.
• Items should not hang from the sprinkler heads.
• Intense heat should not be used near the sprinkler heads.
• Fire detection systems may be temporarily out of service due to utility work performed by the Physical Plant if you have any concerns regarding your fire detection system contact your Safety Officer or Site Manager prior to engaging in any activity where there may be a fire risk.