A study of indoor particle concentrations of less than 10[mu]m in Wellington office buildings : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Building Technology at Massey University
Indoor air pollution can have significant effects on the health of people. Indoor pollutants can exceed outdoor concentrations by 2-5 times, and occasionally more than 100 times. This is significant not only because of occupational indoor exposures, but because in general people spend over 90% of time indoors. Particles are one indoor pollutant that has been linked as a causal factor of the Sick Building Syndrome. Particles can be noxious substances or have noxious substances adsorbed on to them. Of most concern are particles that penetrate to the gas exchange region of the human body as clearance times are often in excess of months. This study explores the relationship between particle concentrations measured indoors and outdoors and the affect of occupant activity on indoor particle concentrations. Particle concentrations were measured indoors and outdoors of four office buildings in Wellington. Indoor particle concentrations as a function of occupancy were assessed and the presence of occupants was shown to increase particle concentrations indoors for the size bands of 5μm and 3μm on a working day. Particles below 1μm were shown to generally behave independent of occupant activity. The concentrations of particles generated during a working day decreased over a period of no occupancy due to deposition and the air exchange rate of the building for the larger size bands of 5μm and 3μm. However below 1μm the pattern of a reduction in particles was not apparent. Overall there was no statistically significant vertical gradient of particles between 1.2m and 1.8m for the particle sizes of 5μm, 3μm, 1μm, 0.5μm, and 0.3μm. Standard filter media were shown to be effective at reducing particle sizes of 5μm and 3μm and less effective with particles below the 1μm range. The operation of the air handling unit over a weekend period resulted in a reduction of the number of fine particles (1μm, 0.5μm, 0.3μm) in the indoor space. The stack effect and its influence on particle transportation throughout the four buildings studied was inconclusive with several factors capable of confounding the collected data. Overall, the results of the study were consistent with other researchers' findings in relation to occupant influence on particle concentrations and filtering efficiency of standard media. Factors that may confound the assessment of the influence of the stack effect on particle concentrations need to be carefully monitored in future studies.