Appendix C: Chemical Fume Hood
General rules for Chemical Fume Hood use:
- No hoods should be used for work involving hazardous substances unless it has an EH&S certification label less than one year old.
- Promptly report any suspected hood malfunctions to EH&S (7-75445). We will coordinate any necessary repairs with Facilities Administration.
- Always keep hazardous chemicals at least six inches behind the plane of the sash.
- Never put your head inside an operating laboratory hood to check an experiment. The plane of the sash is the barrier between contaminated and uncontaminated air.
- Work with the hood sash in the lowest possible position. The sash will act as a physical barrier in the event of an accident in the hood.
- Avoid rapid arm movements, and extraneous drafts such as those caused by opening doors.
- Do not clutter your hood with bottles or equipment. Keep it clean and clear. Only materials actively in use should be in the hood.
- If bulky equipment must be operated in the hood, place on blocks 2"-4" high to permit smooth airflow.
- Clean the grill along the bottom slot of the hood regularly so it does not become clogged with papers and dirt.
- The hood may be operated at reduced flow when appropriate, but should never be turned off. Hood exhaust is vital in maintaining laboratory negative pressure.
- Attach a kimwipe or other 'wigwag' to the hood sash as a visual indicator of airflow.
Some other ventilation control devices such as canopies and slotted exhausts function by capture rather than containment, and have very different specifications. If you use such devices, and are not sure how well they are performing their intended tasks, contact the EH&S office for assistance.
Alternative inhalation control - Respirators
In some circumstances, some form of personal respirator can provide an additional level of protection to the worker. They are vital in 'out-of-control' situations such as spills of extremely hazardous materials, in situations where engineering controls are not available or are precluded by the requirements of the proposed task, where there is a serious potential for release due to equipment failure, or in the handling of particularly hazardous airborne chemicals or microbial agents. Another important application is in the prevention of sensitization to dander by individuals handling laboratory animals. In all cases however the degree of protection afforded by these devices is much less than that of well-designed engineering controls. Selection of an effective device is often complicated, fitting of the device to the user is essential, and strict attention to proper use and maintenance is also very important. As the devices increase inspiratory resistance, medical screening is also necessary. If you feel that respiratory protection may be advisable for a protocol which you are developing, contact the EH&S office for assistance.