How to Calculate the Total Ventilation Rate of a Laboratory Hood

A laboratory hood ventilation system is necessary to protect laboratory personnel or students from exposure to harmful airborne contaminants. The fumigation hood should be able to control and filtrate airborne contaminants at a maximum safety level. The fume hood velocity is important as it must be able to capture and remove dangerous chemical fumes. In order to check the velocity at which your fume hood is working, a velocity indicator should be installed on your hood. The velocity should range from 0.41 to 0.51 meters per second and not go below 0.30 meters per second.

Instructions

• 1

  Install a position sensor monitor on the inside of the laboratory hood. The sensor will monitor the exhaust valve to maintain the velocity at a safe rate and to help ensure that fumes do not leak from under the hood.

• 2

  Install a face velocity indicator, flow alarm or face velocity alarm onto your hood. In addition, make sure the valve on your hood has a fast-acting electronic actuator. When the monitor senses that the low or high limits of velocity have been exceeded, the alarm system will adjust the fast-acting electronic actuator valve to meet the velocity needs.

• 3

  Control the fan speed manually if there is no exhaust valve. Although fans can control the velocity, the safest method is to have an electronic actuator valve along with a sensor and an alarm. These items provide the only accurate means of controlling ventilation velocity in a fume hood.