Fume Hood Performance Indicators
Hood Survey Sticker
Every chemical fume hood on campus should have a survey sticker affixed to the front of the hood in a conspicuous location. Do not use a hood that has no survey sticker. The sticker contains basic information about hood performance as of the most recent survey and should be consulted each time the hood is used.
The [SRM Hood Number] is a unique identifier for the particular hood. Refer to this number when discussing problems with a particular hood.
The Inspection Sticker is aligned on the hood so the arrow is in the proper location for the maximum safe sash position.
The Flow Monitor Reading is the reading of the magnehelic gauge or other continuous monitoring device at the time of the survey.
Static Pressure Gauge (Magnehelic)
Most fume hoods on campus are equipped with static pressure gauges that measure the difference in static pressure across an orifice in the duct, or between the laboratory and the fume hood exhaust duct. Most of the devices are aneroid pressure gauges, such as magnehelics, that are mounted on the front of the hood above the sash.
The gauge is a flow rate indicator with a scale that reads in units of pressure, rather than velocity. Changes in the magnehelic reading are not linearly proportional to changes in face velocity; therefore it should only be used as an index of hood performance.
The magnehelic gauge reading at the time of the most recent hood survey is shown on each fume hood evaluation sticker. A difference of 20% or more in the magnehelic reading from that shown on the sticker is an indication that the flow rate in the duct, and thus the face velocity, may have changed significantly since the last survey. If the user notices such a change, or has any other reason to suspect that the hood is not operating properly, contact Facilities Management at (435)865-8888 for a re-survey of the hood.
[Color Coded and Digital Flow Indicators]
Some hoods are equipped with color indicating devices, or digital flow rate displays rather than or in addition to magnehelic gauges. These devices constantly measure the face velocity of the hood and point to green (for good) or red, or give the actual digital flow rate value to indicate whether or not the hood is functioning properly.
If hood performance is judged to be unsuitable for use with hazardous chemicals, a sticker with this information is placed on the hood instead of the survey sticker.
Hoods are routinely inspected at least annually. If it has been more than a year since the last inspection, contact Facilities Management.
Do not use a hood that has no survey sticker.