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 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. Lab personnel must consider available engineering controls to protect themselves against chemical exposures before beginning any new experiment involving the use of hazardous chemicals.

The maintenance and proper functioning of fume hoods and other protective equipment are shared responsibilities of multiple service groups. Facilities Services (CPFM), 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.

It is the responsibility of lab personnel to immediately report malfunctioning protective equipment, such as fume hoods, or mechanical problems to EHS and Facilities Services (541-346-2319) 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 (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.
• 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 or racks to allow airflow under the item.
• Keep the hood sash at the indicated optimal height to improve 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.
• Never use fume hoods to evaporate hazardous waste. For particularly hazardous substances or those that form toxic vapors, fumes, or dusts, consider using condensers, traps, or scrubbers to prevent environmental release. Consult EHS for guidance.
• Do not exhaust equipment such as vacuum pumps through the hood opening as this disrupts the airflow and prevents sash closure.
• Always practice good housekeeping: clean up spills immediately, regularly wash the working surface and hood sash, and maintain a clean and dry, clutter-free hood.
• In addition to annual inspections, face velocity testing, and vapor capture testing, EHS provides training on the proper use of fume hoods.

Heating Perchloric Acid

Never use heated perchloric acid in a standard fume hood. Doing so can cause the formation of shock-sensitive metallic perchlorate crystals in the ductwork, which could lead to an explosion during maintenance. Heated perchloric acid must only be used in specially designed perchloric acid fume hoods equipped with a wash down system. If you suspect your fume hood has perchlorate contamination or want more information on perchloric acid fume hoods contact the UO Chemical Safety Officer.

Fume Hood Inspection and Testing Program

EHS conducts annual testing and inspection of campus fume hoods. After each inspection, inspection results are recorded on a sticker that is affixed to the fume hood, Facilities Services is notified of any maintenance needs. If your fume hood lacks an inspection sticker or the sticker indicates the last inspection was over a year ago, contact the Laboratory Safety Officer.

Fume hood testing and inspection includes:

• Face velocity testing for compliance with ANSI/AIHA standard Z9.5-2012.
• Visual inspection using the smoke test from ANSI/ASHRAE standard 110-1995, may be performed alongside face velocity testing.

Fume hood operation is classified as acceptable or unacceptable based on average face velocity measurement and smoke test results.

If unacceptable, a warning sign will be posted, and EHS will coordinate repairs with Facilities Services. Hazardous work must be moved out of the hood until repairs are complete.

Installation of New Fume Hoods

Installing a new fume hood requires careful planning and a thorough understanding of the building's existing ventilation systems and capabilities. Improper installation of fume hoods or other capture devices can significantly disrupt ventilation, affecting not only the immediate room but also other hoods and the building-wide system. 

All fume hoods and other capture devices must be installed in consultation with Facilities Services and EHS. New fume hood installations must meet with current design standards and be commissioned by EHS to be included in the ongoing inspection and testing program. To request commissioning of a a new or relocated fume hood contact the EHS Lab Safety Officer. EHS can also provide guidance on the selection, purchase, and inspection requirements for laminar flow clean benches, biosafety cabinets, and ductless fume hoods.

Removal of Existing Fume Hoods

Any removal of fume hoods or other capture devices requires prior consultation with Facilities Services and EHS. This ensures that building ventilation systems are not disrupted and that utility services such as electrical lines, plumbing systems, and water and gas supply lines are properly disconnected.

There may also be concerns about hazardous materials within the fume hood, such as asbestos in the hood or pipe insulation, and 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 with questions about potential asbestos or mercury contamination. 

See the Lab Close-Out section in this document for more information.

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Other Capture Devices

Other engineering controls include vented storage cabinets and local exhaust ventilation (LEV) such as capture hoods (canopy and slot) and snorkels. These systems capture and entrain chemical vapors, fumes, and dusts at the point of generation. 

Examples of appropriate uses include welding, atomic absorption units, vacuum pumps, dry nanomaterials work, and many other operations in the laboratory. Installation of any of these systems must be in consultation with EHS and may require an engineering design to ensure the proper integration with the ventilation systems ductwork.

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Glove Boxes

Glove boxes are sealed enclosures that are designed to protect the user, the process, or both by completely isolating the contents from the external environment. They are typically equipped with at least one pair of gloves attached to the enclosure, allowing the user to manipulate materials inside. Most glove boxes have an antechamber for transferring materials in and out.

Types of Glove Boxes

Controlled Environment (Dry Box)

These create oxygen and moisture free conditions by replacing the internal air with an inert gas, such as nitrogen, argon, or helium, depending on the application. A rotary vane vacuum pump is used to evacuate the original atmosphere. Additional accessories such as a gas purifier, may be used to further reduce oxygen and moisture levels for sensitive operations. There glove boxes are categorized into four classes based on leak tightness with Class 1 having the lowest allowable leak rate. They should be inspected by a service company during commissioning, when the gloves are changed, or whenever glove box performance is in question. 

Ventilated Glove Box (Filtered Glove Box)

These glove boxes have HEPA or ultra-low particulate filters on both the inlet and outlet sides of the box along with a blower to circulate the air. They protect the user through filtration and may also be ducted to building exhaust systems through a thimble connection. In cleanroom applications, airflow can be reversed to create positive pressure and protect the process or product.

Regular maintenance and inspection is essential to ensure glove boxes are providing adequate protection to users, the environment, and/or the product or process. Maintenance schedules and certification intervals 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 glove boxes – Third Edition. AGS-G001-2007.