Engineering controls are considered the first line of defense in the laboratory for the reduction or elimination of exposure to hazardous chemicals. Examples of engineering controls used in laboratories at the University of Oregon include local exhaust ventilation, chemical fume hoods, biosafety cabinets, glove boxes, and other containment enclosures such as ventilated storage cabinets.
The OSHA Laboratory Standard requires that "fume hoods and other protective equipment function properly and that specific measures are taken to ensure proper and adequate performance of such equipment." General laboratory room ventilation is not adequate to provide proper protection against bench top use of hazardous chemicals. Laboratory personnel need to consider available engineering controls to protect themselves against chemical exposures before beginning any new experiment(s) involving the use of hazardous chemicals.
The proper functioning and maintenance of fume hoods and other protective equipment used in the laboratory is the responsibility of a variety of service groups. Facilities Services, EHS, and other groups service equipment such as mechanical ventilation, fire extinguishers, emergency eyewashes, and showers. Periodic inspections and maintenance by these groups ensure proper functioning and adequate performance of these important pieces of protective equipment.
However, it is the responsibility of laboratory personnel to immediately report malfunctioning protective equipment, such as fume hoods, or mechanical problems to EHS and Facilities Services as soon as any malfunctions are discovered.
CHEMICAL FUME HOODS
Fume hoods and other capture devices are used to contain the release of toxic chemical vapors, fumes, and dusts. Benchtop use of chemicals that present an inhalation hazard is strongly discouraged. Fume hoods are to be used when conducting new experiments with unknown consequences from reactions or when the potential for a fire exists.
To achieve optimum performance, maximum personal protection, and reduced energy usage when using a fume hood:
- Ensure the fume hood is working by checking the tell-tale flagging tape (ribbon hanging from hood sash) and air monitoring device if the hood is equipped with one. DO NOT use an improperly working fume hood for potentially hazardous work.
- If the fume hood is not working properly, let other people in the lab know by hanging up a Do Not Use sign on the hood.
- Work at least six inches inside the hood. This provides for the greatest amount of capture and removal of airborne contaminants. Also, do not place items on the airfoil (intake) or work with chemicals at the face of the hood.
- Do not block the baffles at the back of the hood. These allow for proper exhausting of contaminants from the hood.
- Place any large equipment or items in the hood on raised blocks to allow airflow under the item.
- Keeping the hood sash lowered improves the performance of the fume hood by maintaining the internal vortex and containment. It also helps to conserve energy.
- Keep the fume hood sash completely closed whenever the fume hood is not being used.
- Do not use fume hoods to evaporate hazardous waste. Evaporating hazardous waste is illegal.
- For work involving particularly hazardous substances or chemicals that can form toxic vapors, fumes, or dusts, the hood or equipment within the hood may need to be fitted with condensers, traps, or scrubbers in order to prevent the vapors, fumes, and dusts from being released into the environment. Consult EHS for advice.
- Do not exhaust items such as vacuum pumps through the face of the fume hood as this will disrupt the airflow into the hood and may break containment. This will also not allow for the sash to be fully closed.
- As with any work involving chemicals, always practice good housekeeping and clean up all chemical spills immediately. Be sure to wash both the working surface and hood sash frequently and always maintain a clean and dry work surface that is free of clutter.
- In addition to annual fume hood inspection, face velocity testing, and dry ice capture testing, EHS provides training on the proper use of fume hoods.
Fume Hood Inspection and Testing Program
EHS has the responsibility for the annual testing and inspection of fume hoods on campus. After each inspection, an inspection sticker is affixed to the fume hood, Facilities Services is notified of all hoods that require maintenance. If your fume hood does not have an inspection sticker or if the existing inspection sticker on your fume hood indicates a year or more has passed since the hood was last inspected or for other questions please contact the Laboratory Safety Officer at 346-2864.
Fume hood testing and inspection consists of the following:
- The face velocity will be tested for compliance with American National Standards Institute (ANSI) and American Industrial Hygiene Association (AIHA) standard Z9.5-2012.
- A visual inspection using the smoke technique from the ANSI/American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) standard 110-1995, will be performed in conjunction with face velocity measurements.
- Hoods will be classified as acceptable or unacceptable based on the average face velocity measurement and result of the smoke test.
- If a hood is found to be unacceptable, a warning sign indicating the hood did not pass inspection and does not provide optimum protection will be attached in a conspicuous location. EHS will make the repair arrangements with Facilities Services, laboratory occupants will have to move hazardous work out of the failed hood until repairs are completed.
Installation of New Fume Hoods
Installation of a new fume hood requires careful planning and knowledge of the existing building ventilation systems and capabilities. Improperly installed fume hoods or other capture devices can seriously disrupt the existing ventilation system and have a negative impact in the immediate room, other fume hoods, and the ventilation system throughout the building.
All fume hoods and other capture devices must be installed in consultation with UO Facilities Services and EHS. All new installations of fume hoods must comply with current design standards and be commissioned by EHS to be included in the inspection and testing program. To request a new or relocated fume hood be commissioned please contact the EHS Lab Safety Officer at 346-2864. EHS can provide information regarding the selection, purchase, and inspection requirements for laminar flow clean benches, biosafety cabinets, and portable fume hoods.
Removal of Existing Fume Hoods
Any removal of fume hoods and capture devices requires prior consultation with Facilities Services and EHS. This is necessary to ensure building ventilation systems are not affected by removal of fume hoods and capture devices, and so utility services such as electrical lines, plumbing systems, and water and gas supply lines are properly disconnected.
There is an additional concern for the presence of asbestos within the fume hood itself, and potentially in any pipe insulation associated with the ductwork and/or mercury in cup sinks. Any asbestos must be properly removed and disposed of by a certified asbestos removal company. EHS can assist laboratories with the cleanup of any mercury contamination. Contact EHS at 346-3192 for more information or questions about potential asbestos or mercury contamination. See the Lab Close-Out section in this document for more information.
OTHER CAPTURE DEVICES
Engineering controls besides the fume hood include compressed gas cabinets, vented storage cabinets, and local exhaust ventilation (LEV) such as capture hoods (canopy and slot) and snorkels, which capture and entrain chemical vapors, fumes, and dusts at the point of generation. Examples where these devices would be appropriate are welding operations, atomic absorption units, vacuum pumps, work with dry nanomaterials, and many other operations in the laboratory. Installation of any of these must be in the consultation of EHS and may include an engineering design to ensure the proper connection into the ventilation systems ductwork.
Glove boxes are sealed enclosures that are designed to protect the user, the process or both, by providing total isolation of the contents from the outside environment. They are usually equipped with at least one pair of gloves attached to the enclosure. The user manipulates the materials inside using the gloves. Typically, a glove box has an antechamber that is used to take materials in and out of the box.
Types of Gloveboxes:
1) Controlled Environment (dry box) - These create oxygen and moisture free conditions by replacing the air within the box with an inert gas, such as nitrogen, argon, or helium, depending on the type of materials to be worked with. A "rotary vane vacuum pump" is used to remove the atmosphere. Additional accessories may be used, such a gas purifier, to further reduce oxygen and moisture levels for particularly sensitive operations. There are four types of this type of glovebox based on their leak tightness. Class 1 has the lowest hourly leak rate. This should be inspected by a service company during commissioning, when the gloves are changed, or when there appears to be a problem with the functioning of the glovebox.
2) Ventilated Glovebox (filtered glovebox) - These have filters, either HEPA or ultra-low particulate, on the inlet and outlet ends of the box and a blower to circulate the air. These provide protection to the user through this filtration and also if the exhaust is connected to building exhaust through a thimble connection. These can have serve in cleanroom applications by reversing the airflow in the chamber to positive pressure.
- Regular maintenance and inspection is essential to ensure that a glove box is adequately protecting the user, the environment and/or the product/process. Routine maintenance procedures and the frequency of inspection (or certification) should follow the manufacturers and regulatory recommendations.
- There are various tests that can be performed on glove boxes, the suitability of which depends on the glove box and the application. Tests may include pressure decay (for positive pressure), rate of rise (for negative pressure), oxygen analysis, containment integrity, ventilation flow characterization, and cleanliness. The source of a leak can be identified using a Mass Spectrometer Leak Detector, ultrasound, the soap bubble method or use of an oxygen analyzer. For an in-depth discussion of glove boxes and testing, see: AGS (American Glove Box Society) 2007 Guide for gloveboxes – Third Edition. AGS-G001-2007.
Heating Perchloric Acid
DO NOT use heated perchloric acid in a standard fume hood. If heated perchloric acid is used in a standard fume hood (without a wash down function), shock-sensitive metallic perchlorate crystals can form inside the ductwork, which could result in causing an explosion during maintenance work on the ventilation system. Use of heated perchloric acid requires a special perchloric acid fume hood with a wash down function. If you suspect your fume hood has perchlorate contamination or would like more information on perchloric acid fume hoods, then contact the UO Chemical Safety Officer at 541-346-9299.