Hello Eskimo2

You can lash a balometer/ hood together but consider these issues before you do.

1) how are you going to calibrate it.

(different hoods at different air volumes can produce different resistance characteristics)

2) Anyone involved in validation/commissionig should be asking what instrument you used and prove it is calibrated.

3) Homemade hoods tend to be heavy and cumbersome.

4) You need a REASONABLE seal around the diffuser/grille

5) Use a flow grid if possible, which should cover a high percentage of the hood apeture you intend to measure from. ( avoid using single point equipment i.e. pitot, hot wire and avoid small diameter anemometers). The whole idea is to measure as much of the volume at the apeture as possible in an instant.

If you still think it is worth building one then before using it in anger cross reference at regular intervals to a known reading from a calibrated industry approved meter and still be prepared to have your figures thrown back at you.

It can get pretty nasty when consultants and commissioning engineers start getting bitchy about their equipment.