What do fume hoods do

Lab directors must obtain approval from EHS to purchase a ductless fume hood. If a lab director is approved to purchase a ductless fume hood, the following work practice controls must be implemented in the laboratory and during research activities. Skip to content. Search for: Search. Fume Hood Use A fume hood is a ventilated, enclosed work space intended to capture, contain, and exhaust harmful or dangerous fumes, vapors, and particulate matter generated by procedures conducted within the fume hood.

Fume Hoods must have the air flow checked and be certified: Once a year by EHS After maintenance work is performed new motor, repairs, modifications, relocation, a new fume hood being installed, etc. The glass is designed to spider instead of shatter. The sash should be closed when you are not working in the hood. Keep your face outside of the fume hood. The sash acts as a barrier and is there for protection while completing hazardous work.

Place large equipment on blocks. This will allow air to flow beneath it and enable the fume hood to do its job. Do not disturb the airflow. Using exterior fans near the fume hood opening may cause airflow disturbances, which will alter the effectiveness of the fume hood.

Likewise, walking near the hood opening or making quick motions in or out of the hood may have a similar effect. Rapid movements can create sufficient turbulence to disrupt the inward flow of air into the hood and may result in worker exposure. Shut the sash. It is necessary to have the fume hood open when working inside of it, but when not in use, keep it closed. When the sash is closed, energy will be conserved.

A fume hood is a ventilated enclosure in which gases, vapors and fumes are contained. An exhaust fan situated on the top of the laboratory building pulls air and airborne contaminants through connected ductwork and exhausts them to the atmosphere. The typical fume hood found in Princeton University laboratories is equipped with a movable front sash and an interior baffle. Depending on its design, the sash may move vertically, horizontally or a combination of the two and provides some protection to the hood user by acting as a barrier between the worker and the experiment.

We do not recommend ductless fume hoods. We do not believe ductless fume hoods provide reliable protection against chemical exposure, and think they may, in fact, give workers a false sense of security. The ductless hood's appeal is largely economic because it does not require the expensive ductwork that traditional hoods need to exhaust fumes to the outside. In many cases, the filter is designed for specific chemicals and will not protect against the variety of current and future chemicals used in a typical research university lab.

The problems associated with breakthrough and with desorption of vapors from the absorbent material plague ductless fume hoods. Therefore, depending upon the amount of use, annual maintenance costs to the owner could exceed several hundred dollars.

Internal blowers for ductless hoods have also been known to be loud and prevent effective communication within the lab. Fume hoods, ducted or filtered, should only be installed in fully exhausted labs with minimum dilution ventilation rate of 6 to 8 air changes per hour. Ventilation codes do not allow general return or exhaust air from a laboratory space with a fume hood to be recirculated to classrooms or offices.

If a department is purchasing or owns a ductless fume hood, they must develop written laboratory standard operating procedures SOPs that must include the following:.

Each hood should be equipped with a monitoring device used to continuously measure air flow, and provide a visible reading to the hood user. It is important to the health and safety of the laboratory occupants to pay close attention to the digital or posted reading. A broken or missing performance indicator may result in lab occupants being unaware of air flow changes, and increasing the risk of chemical exposure. If you believe that your hood is missing a performance indicator, your current device has been damaged, or is out of range; please contact REM immediately to have one installed.

Inclined Manometer : Detection system mounted in a slightly inclined position; capable of measuring pressure above and below atmospheric. REM supplies the red gauge oil used to quantify the velocity pressure measured by a change in differential pressure from total atmospheric. REM will calibrate the device when air velocity measurements are inspected annually and record the reading on a sticker along with the date.

Continuing to use a fume hood with high or low flow poses a risk to the user and lab occupants if the chemicals are not adequately contained and exhausted. Magnehelic Differential Pressure Gauge : Monitoring device that measures the difference in differential pressure across an orifice in the duct or between the laboratory and the fume hood exhaust duct.

They are mounted on the outside of the hood and detect pressure differences from atmospheric, operating with an aneroid pressure gauge. REM will calibrate the Magnehelic at the annual inspection of the fume hood and record the location of the pointer for the official reading along with the date.

Sash position is correlated to the air velocity at that sash opening area to determine face velocity. Digital monitors will display velocity on a screen, while some only contain an alarm system and is color coded accordingly:. If your fume hood control device is going into alarm mode please contact REM so we can assess the air velocity of the fume hood. A REM representative will determine if the air flow is within the recommended range and either submit a work order for repair or suggest that the digital monitoring device be calibrated.

If a monitoring device is not reading accurately and needs serviced, it may alarm even if the air velocity is within the safe zone. Calibration of digital monitors is serviced by the designated Zone Maintenance to your area by submitting a Request for Services, 18A work order. Upon completion of the hood inspection, REM will record:. This information will be labeled on a yellow sticker and placed at the indicated approved working height related to that face velocity measurement.

Users should raise the sash to the working height indicated by the black arrow on the label when operating the hood.