Settled Dust and Airborne Particulate Pilot Study
INTRODUCTIONThe Trane Residential Systems CleanEffects™ air cleaning system reduces accumulation of dust on surfaces in homes according to anecdotal reports received by Trane from customers who have purchased the product. Environmental Health & Engineering Inc. (EH&E) conducted a pilot investigation to evaluate the accuracy of these reports. Settled dust and airborne particulate matter (PM) levels were measured in five occupied homes during periods when the air cleaner was on and off. The pilot investigation was part of a larger field campaign that involved nine single-family homes in four states. Results of the larger campaign are presented in the EH&E report dated July 31, 2008.
MATERIALS AND METHODSFive single-family homes in the Boston area with the air cleaner were recruited to participate in the study over four winter and spring months. Settled dust samples were collected in three of the five homes. Two sets of samples were collected at each location, the first set was collected after the air cleaner operated for two weeks, and a second set was collected following two weeks when the air cleaner was not operated. Air samples for PM mass and elemental analysis were collected in three homes, one of which also was used for the settled dust investigation. Two sets of samples were collected from one indoor and one outdoor location, the first set of samples was collected while the air cleaner was operating and a second set was collected while the air cleaner was not operating.
RESULTS AND CONCLUSIONSSampling was conducted between January and April 2008, in homes in the Boston area. Settled house dust samples were collected from up to five locations in three homes. Indoor and outdoor PM samples that were analyzed for elemental composition were collected in three different homes.
The primary conclusions of the pilot investigation are that:
• Fifty percent less dust accumulated when the air cleaner was on than when it was off, on average.
• Airborne PM levels were lower indoors when the air cleaner was on compared to when it was off. Specifically:
- The ratio of indoor PM to outdoor PM was lower when the air cleaner was on compared to when it was off in all three homes studied.
- A marker of PM of ambient origin, sulfur, was lower when the air cleaner was on compared to when it was off, in two of the three homes.
- Operation of the air cleaner resulted in lower indoor to outdoor ratios for components of dust, such as silica in all three homes, and elements generated indoors, such as copper, in two of the three homes studied.
The air handling units (AHU) and air cleaners in the five homes were set to run only when heating or cooling was called for by the thermostat. If the AHUs had been equipped with a variable speed fan capable of running at full speed during periods of heating and cooling demand and at half-speed during all other times, even greater reductions in settled dust and PM attributable to the operation of the air cleaner may have been observed.
These results are consistent with results obtained from previous EH&E investigations. For example, testing by EH&E in an unoccupied test home demonstrated that the air cleaner is highly effective at reducing indoor concentrations of PM generated indoors and reducing levels of PM that infiltrates into the home from outdoors. Similarly, indoor air quality modeling studies conducted by EH&E show that the air cleaner is effective at reducing levels of allergens in the home (Myatt et al., 2008). Considered together with the results of previous studies, the results confirm that the use of the air cleaner will substantially reduce accumulation of dust indoors and indoor levels of particulate air pollution. This study provides further evidence that the air cleaner lowers exposure to PM indoors, including bioaerosols. Further research is required to evaluate potential health benefits that may accrue from the lower pollutant exposure afforded by the air cleaner.
For a copy of the complete study, go to www.trane.com/dustless.
Publication date: 12/15/2008