Microcomputer-aided measurement of air change rates

Air change rates are measured by a non-dispersive one-beam IR gas analyzer using the decay and constant-emission methods with nitrous oxide as tracer gas using a RS-232-C interface to a microcomputer.

Abstract

Air change rates are measured by a non-dispersive one-beam IR gas analyzer using the decay and constant-emission methods with nitrous oxide as tracer gas. Disturbing influences due to H2O and CO2 are low. The analyzer is coupled via a RS-232-C interface to a microcomputer, which is programmed to service the following functions: (1) calibration, (2) preparation and control of measurements, (3) recording, displaying and storing of data, (4) evaluation of results, and (5) error analysis. The implemented programs provide an instant access to results. The whole equipment is installed in compact form on a mobile rack. Measurements have been taken in a university laboratory to examine air change rates with (1) closed door and window, (2) open door only, and (3) tilted window only. Typical results are given and show where the decay method or the constant-emission method is more appropriate.