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Chemical Safety
CHEMICAL FUME HOODS & VENTILATION
Chemical fume hoods are the primary engineering control for capturing and removing hazardous airborne contaminants in laboratories. When used properly, the fume hood will minimize or eliminate exposure, as well as reduce the risk of injury or damage due to explosions, spills, etc. To learn more about fume hoods, how to determine the fume hood is safe to use and guidance for implementing safe work practices, please view the following educational module: Proper Practices for Chemical Fume Hood Use.
There are over 1,000 chemical fume hoods used by faculty, staff, and students at UVA. Every hood is surveyed annually by Environmental Health & Safety (EHS).
These surveys are critical in determining whether or not the most important piece of safety equipment in a lab is performing satisfactorily.
The sticker on the face of the hood has instructions on how to operate the fume hood and provides contact information for repair or re-surveys. Sticker color may change from year to year. Modification of the local exhaust ventilation system without approval is prohibited, as changes made to the system may result in unsafe conditions.
The purpose of this document is to provide guidelines for the selection, installation and testing of chemical fume hoods (CFHs) in UVA owned and operated facilities. Also included within this document are suggestions for the optimal placement of CFHs, general room ventilation characteristics and other recommended design elements pertinent to achieving optimal CFH performance.
See our Frequently Asked Questions about Chemical Fume Hoods.
Use a chemical fume hood when handling chemicals that have high acute toxicity, are carcinogens, mutagens or are reproductive toxins; anytime your work involves potential exposure to chemicals with a NFPA Health rating of 3 and 4; chemicals are flammable, corrosive or irritating, reactive, potentially explosive; or where heating or agitation may cause chemicals to spatter or aerosolize. Chemicals with particularly low odor thresholds, (e.g., beta-mercaptoethanol, thiols, etc.) should also be handled in a chemical fume hood, regardless if hazardous or non-hazardous.
Use a chemical fume hood when the chemical's safety data sheet indicates under Section 8 Exposure Controls, "provide exhaust ventilation or other engineering controls to keep the airborne concentrations of vapors below their respective threshold limit value".
There may be instances where there is only a very low risk of exposure to the chemicals described above (e.g., use of minimal quantities in a closed system). A risk assessment can be performed to determine if a chemical can be safely handled outside of a chemical fume hood. Contact EHS for assistance with a risk assessment.
Consider upgrading to a glove box or other isolation device for particularly hazardous substances, toxic gases, and highly reactive or explosive/pyrophoric materials, as chemical fume hoods are, under the best of circumstances, only certified to a containment performance of less than 0.1 part per million (ppm) leakage rate.
The use of perchloric acid, particularly in concentrated form (>72%) and used above room temperature, can result in the accumulation of explosive perchlorates on chemical fume hood surfaces and inside ductwork. It is dangerous to use perchloric acid in a conventional fume hood and where other materials (organics, flammables) could mix with perchlorates, resulting in an explosion that could be touched off by friction from simply adjusting the panels and baffles in the hood. Work that involves heating any concentration of perchloric acid or evaporating concentrated perchloric acid must be performed in a perchloric acid fume hood that is designed specifically for use with materials that can deposit shock-sensitive crystalline materials. These hoods are constructed throughout of stainless steel and equipped with water wash-down capabilities.
The water spray should be used whenever perchloric acid is heated in the hood. If a conventional fume hood has been exposed to heated perchloric acid, tests must be conducted to determine if explosive perchlorates have formed on the hood walls and duct system. This must be completed before any inspection, cleaning, maintenance, or any other work is done on any part of the hood interior or exhaust system.
Based on these special needs, which are not provided for in most laboratories, perchloric acid may not be handled in concentrated form (>72%) or manipulated above room temperature (i.e., heated) in any laboratory that is not specially equipped to address the associated hazards.
Specialty perchloric acid hoods are in Jesser Hall and in Wilsdorf Hall. Contact EHS if you believe you need assistance in gaining access to one of these specialty hoods.
Ductless fume hoods are stand-alone enclosures that use carbon and/or HEPA filters to remove fumes, vapors and particulates from air drawn through the device and then discharge the filtered air back into the laboratory.
Due to the great variety of chemicals that might be used in a research setting, it is difficult to predict the effective lifespan of ductless fume hood filters. Accordingly, EHS does not generally recommend the use of ductless fume hoods in research laboratories.
Ductless fume hoods should never be used to contain highly toxic, flammable, explosive or carcinogenic chemicals; however, they may be necessary as a temporary measure to contain small quantities of chemicals when proper engineering controls (i.e., ducted chemical fume hood or local exhaust ventilation) are unavailable.
Investigators may request EHS approval for use of ductless fume hoods by submitting a written standard operating procedure (SOP) describing the parameters and conditions for safe use. The SOP should include the following information:
EHS will conduct a hazard evaluation and issue approval by applying a certification label to the device and reassess certification on an annual basis.
Investigators using ductless fume hoods are responsible for training their personnel on the safe use and limitations of these devices. Modification to approved chemical procedures conducted in ductless enclosures require an updated hazard evaluation by EHS.
Chemical fume hoods are highly energy-intensive as they continuously remove conditioned air from a space. Constant volume chemical fume hoods can use more than 3 times as much energy as a single-family home on an annual basis. The energy required for filtering, moving, cooling or heating, and cleaning air is the largest cost in lab facilities. Innovations in chemical fume hood technology and design have succeeded in reducing airflow through chemical fume hoods while maintaining, or increasing, safety and performance.
Variable air volume (VAV) chemical fume hoods exemplify an innovation in chemical fume hood technology.
VAV systems adjust the amount of air that passes through a chemical fume hood while maintaining a minimum velocity for safety. The reduction in air passing through the chemical fume hood when the sash is lowered results in a reduction of outside air that must be reconditioned to replace the air exhausted. The less outside air that must be conditioned results in lower building costs.
Shut the Sash (energy saving) competition was initiated at UVA in October 2017 by the Green Labs Program and is offered annually by UVA Sustainability.
