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Lab ventilation controls are intended to minimize employee exposure to hazardous chemicals by removing air contaminants from the work site. There are two main types of ventilation controls:
General (Dilution) Exhaust: a room or building-wide system that brings in air from outside and ventilates within. Laboratory air must be continually replaced, preventing the increase of air concentration of toxic substances during the workday. General exhaust systems are not recommended for the use of most hazardous chemicals with respiratory hazards.
- Local Exhaust: a ventilated, enclosed workspace intended to capture, contain, and exhaust harmful or dangerous fumes, vapors, and particulate matter generated by procedures conducted with hazardous chemicals. These may include fume hoods and biological safety cabinets.
A. Proper Use of Local Ventilation Systems (Fume Hoods):
For use of hazardous chemicals warranting local ventilation controls, the following guidelines should be observed:
Fume Hood Safe Work Practices
- Conduct all operations inside a fume hood if they have the potential to generate hazardous gasses, vapors, fumes or air contaminants at or above Permissible Exposure Limits or Threshold Limit Values.
- Do not put your head or upper body into the hood, except during initial setup and before hazardous materials are present.
- Hoods should not be used for permanent storage of hazardous materials or equipment. With the exception of certain hazardous waste containers, all chemicals should be stored in an appropriate location outside of the hood.
- Hazardous materials and equipment should be placed at least 6 inches inside the hood for proper containment of chemical vapors.
- Equipment inside the hood should be placed so as to not block airflow through slots in the baffle. Blocks may be necessary under large equipment to allow air to flow to the rear baffle.
- The fume hood safety-glass sash should be kept below the stopper at approximately 18 inches. The hood sash should be set at this point for procedures which could generate toxic aerosols, gases, or vapors. In general, the sash height should be set at a level where the operator is at least partially shielded from any explosions or violent reactions and where optimum airflow dynamics are achieved. If a fume hood has no markings regarding sash height or inspection dates, please contact Lab Safety to arrange for an inspection.
- Alarms: Most hoods are equipped with flow sensors. They will generally alarm if flow is too low or too high. Typically the problem corrects itself, possibly after adjusting sash height. If an alarm continues, stop using the hood and contact a Lab Supervisor or Facilities Services. The alarm can be muted, however the hood should not be used until the proper flow rate is shown on the monitor.
- Emergency Purge: In the event or a spill, smoke, or other unintended vapors, press the emergency button on the sensor to increase to maximum fan speed.
- Completely close the hood when not in use to reduce energy consumption.
- Minimize foot traffic and other forms of air disturbances past the face of the hood.
- Do not have sources of ignition inside the hood when flammable liquids or gases are present. Always place heat sources to the rear of the hood.
- Check that the digital air flow monitor reads 70 fpm or greater prior to each use to assure that the hood is functioning. Never work with hazardous chemicals or biohazards if the required ventilation system is not working.
- Hoods should not be routinely used as a waste disposal mechanism for volatile materials.
- Do not block air supply vents or exhausts in the room.
- Perchloric Acid Hoods: Use of perchloric acid must be done in a designated hood. Currently perchloric acid use is discouraged and no hoods have been designated.
- Always use proper personal protective equipment when working with chemicals in a hood. Hoods are used when a chemical or a procedure as a greater than usual potential is especially dangerous, so eye protection, gloves, and lab coats should be worn.
B. Proper Use of Biological Safety Cabinets
The Biological Safety Cabinets (BSC's) are used to provide containment of infectious splashes or aerosols generated by many microbiological procedures. BSCs use High Efficiency Particulate Air (HEPA) filters to protect personnel and products inside the BSC from contamination from aerosols and particulates. They also protect the laboratory by isolating and containing the work in progress within the BSC.
Properly maintained Biological Safety Cabinets are used whenever:
- Procedures with a potential for creating infectious aerosols or splashes are conducted. These may include centrifuging, grinding, blending, vigorous shaking or mixing, sonic disruption, opening containers of infectious materials that may be under pressure, inoculating animals intranasally, and harvesting infected tissues from animals or eggs.
High concentrations or large volumes of infectious agents
Guidance for safe use of biological safety cabinets:
- Never use chemicals with the potential to generate hazardous vapors. The HEPA filters are intended only to remove particulates and biological agents.
- Never work in or near the hood with the ultraviolet light turned on. UV light can damage eyes and exposed skin very quickly. Only use the light for the minimum period of time necessary for disinfection, never more than 15 minutes. Note: NIH, CDC, and ABSA all discourage the use of UV for disinfection.
- Work surfaces should be decontaminated with an appropriate disinfectant on a routine basis, after work with infectious materials is finished, and especially after spills, splashes, or other contamination by infectious materials.
- If the unit is not left running continuously, turn the blower on and air purge for at least five minutes to remove airborne contamination before the next use.
- Each laboratory should develop procedures which identify the hazards that will or may be encountered, and which specifies practices and procedures designed to minimize or eliminate risks.
- Laboratory personnel must receive appropriate training on the potential hazards associated with the work involved, including the necessary precautions to prevent exposures, and the exposure evaluation procedures.
C. Standards for Inspection
- Each user is responsible for ensuring that fume hoods and biological safety cabinets are operating properly prior to use.
- GVSU will conduct annual inspections of fume hoods to evaluate the airflow, sash, and overall condition of each hood.
- Every three years each fume hood will be certified by a third party inspection contractor.
- BSCs must be certified annually or after repairs.
Hoods and BSCs will be posted with the most recent date of certification. Notify Facilities Services or Lab Safety for operation or maintenance concerns.