The National Institute for Occupational Safety and Health (NIOSH) and the U.S. Army, Construction Engineering Research Laboratory (USA-CERL) have collaborated on a project that examines the influence of heating, ventilation, and air-conditioning (HVAC) system operational parameters on the levels of microorganisms found in a simulated office space. In these experiments, fungi were collected as representative microorganisms using side-by-side sieve and slit samplers. Experiments at USA-CERL demonstrated that fan coil units are a major source of fungal aerosols in the built environment.
A matched pair of identical mobile homes, one supplied with electric heating and cooking utilities and the other with propane gas utilities, were used to evaluate, over a 14-month period, various factors which may affect indoor formaldehyde c
Formaldehyde concentrations and ventilation rates in Finnish housing were measured. Results are discussed with reference to the recommended minimum ventilation rate of 0.5 ach.
Results are given of the effect of ventilation rate, duct length and particle concentration on ion concentration under laboratory conditions. The effect of electrostatic fields is discussed.
Measurements of radon and radon daughters in 11 buildings in five states, using active or passive solar heating showed no significant increase in concentration over the levels measured in buildings with conventional heating systems. Radon levels in two buildings using rock storage in their active solar systems exceeded the U.S. Nuclear Regulatory Commission's 10 CFR 20 limit of 3 pCi/l for continuous exposure. In the remainder of the buildings, radon concentrations were found to be at levels considered to be normal.
A minimum ventilation rate of 25 m3 per person per hour or 1.5 air changes per hour for homes in the Netherlands is discussed. Difficulties in stimulating awareness of adequate ventilation amongst residents in homes with low ventilation rates of 0.5 to 1 ach is covered.
To develop effective monitoring and control programs for indoor radon it is important to understand the causes of the broad range of concentrations that have been observed. Measurements of indoor radon concentration and air-exchange rate in dwellings in several countries indicate that this variability arises largely from differences among structures in the rate of radon entry.
Compares the air change rates measured using the decay method with several different tracer gases. The tracer gas measurements were conducted in atightly sealed room where constant air leakage rates, ranging from 0.05 to 1 air change per hour could be maintained using an exhaust fan. The tracer gases investigated were CH4, CO, CO2, N2O and SF6. The agreement between tracer gas measurements and measured flow rates of the exhaust fan was very good for CH4, CO and N2O.
Volatile organic chemicals in indoor air of a home-for-the-elderly and a new local government office building were identified and quantified using Texax GCR samplers and capillary gas chromatography/mass spectrometry analysis. Over three hundred chemicals were tentatively identified in indoor air of thehome-for-the-elderly. Comparison of night-day levels were made. The new office building was also part of a longitudinal study which revealed a rapid decrease in levels with time for some chemicals (after completion) while others increased.
The problem of indoor air pollution has many facets, ranging from excess humidity, mould and insects over emissions from gas boilers to high levels of various chemicals in tight buildings. The common denominator of all these problems is the existence of several sources of pollution inside a volume of relatively low dissipative capacity. Where the resulting concentration from a single substance exceeds an already established hygienic standard regulatory measures are straightforward. Assessing the risk of several substances being present at the same time is still difficult.
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