Air Velocity Measurement Equipment Applications

In studies where air movement is of chief concern several equipment options are available. Based on answering a few simple questions you can determine which one suits your unique needs.

  • Do you have a general idea of the flow rate you will be monitoring?
  • Is it higher than 4,000 feet per minute (FPM)?
  • Do you have an idea of what the air temperature range is?
  • Is it 100 degrees or 200 degrees, Celsius or Fahrenheit?
  • What is the size of the opening where you will be testing?
  • Is the flow to be monitored in a pipe or duct?

Once you have answered these questions a proper unit can be suggested. For instance, if you have high temperatures that are over 200 degrees Fahrenheit, the TESTO 445 is a good choice. If below 200F, either the Testo units or the Dwyer 471 would be sufficient. Are your expected flow rates over 12,000 FPM? Then you should use the Dwyer 471, if below you can use either the Testo 445 or Dwyer 471 unit.

If you need to drill an opening to insert the probe head inside, be sure to decide which monitor you wish to use during the study first so you drill the correct diameter. You do not want to make the opening too small or large; this could allow flow to possibly escape between the opening and your probe. Be sure to also check and see how far your instrument's probe may need to be inserted into an opening.  If the area where the measurement is taken on the probe is not fully exposed to the airflow, inaccurate readings may occur. Specifications of the probes are easy to determine and are usually found in the instrument's manual.

If you’re ever required to take readings in cubic feet per minute (CFM) you will need to use an instrument like the Testo 400 or 445. When determining CFM readings, proper measurements of the duct or pipe sizes must be programmed into the instrument. The Testo model flow meters are both capable of this.

The monitors mentioned above operate by using two different types of technologies to determine flow. Our rental Testo units use a vane, which is a spinning propeller-like part to determine flow; the faster it spins the higher your recorded flow rate will be. The Dwyer uses a thermal probe which utilizes a fine heated wire element to determine flow. The wire is heated above that of ambient conditions so when placed into an air flow it cools. The rate of change across the wire is quantified in feet per minute (FPM) or meters per second (MPS).

Typical studies that employ the use of these air measurement devices are HVAC efficiency studies, remediation pilot test studies, AFVR testing and industrial hygiene studies.