tracer gas

This paper presents a quantitative estimate of the error of the decay and constant concentration method. A number of tests were carried out in an indoor test house located in the laboratory hall at the National Swedish Institute for Building Research. The relevant meaning of the concept of air-exchange rate is discussed and an appropriate terminology is suggested. The theoretical background, based on a multi-cell model, of the two tracer gas methods is given.

Large, multicelled and naturally ventilated buildings pose many inherent problems for the measurement of overall infiltration rates using tracer gases. Considering a single tracer gas decay technique, the most obvious problems are: (a) local variations in infiltration, (b) imperfect internal mixing of the air, and (c) practical difficulties in distributing (ie, seeding) the tracer gas and subsequently obtaining air samples.

Mechanical ventilation systems in large office buildings are designed to meet space conditioning loads and to maintain acceptable indoor air quality. In order to achieve acceptable air quality, the ventilation systems are designed to bring in a mlnimrm amount of outside air whenever the building is occupied.

A new method for measuring interzonal air movement, using up to four different tracer gases simultaneously, has been developed at the Polytechnic of Central London and tested in a solar air-heated experimental house in Peterborough, UK. 

Tracer gas techniques for measuring airflows in buildings fall into three categories - dilution, constant injection, and constant concentration. 

Large, multicelled, and naturally ventilated buildings pose many inherent difficulties for the measurement of overall infiltration rates using tracer gases. 

Air exchange rates were measured in the National Archives Building under various combinations of temperature and wind speed. The average air exchange rate under normal operation of the HVAC system was 0.9 h-1 for an average temperature difference.

This paper describes the procedures used in residences for rapid grab-sample and time-dependent measurements of the air-exchange rate and radon concentration: the radon source magnitude is calculated from the results of simultaneous measurements of these parameters. Grab-sample measurements in three survey groups comprising 101 US houses showed the radon source magnitude to vary approximately log-normally with a geometric mean of 0.37 and a range of 0.01 to 6.0 pCi/l/h.

A method for following air movement within buildings, which uses several different tracer gases simultaneously, has been developed.

The Aardvark automated system has been developed for continuously measuring the air-exchange rate and 222Rn (radon) concentration in an occupied residence. The air-exchange rate is measured over 90 min intervals by tracer gas decay using sulphur hexafluoride as the tracer gas.