Skip common site navigation and headers
United States Environmental Protection Agency
Exposure Research
Begin Hierarchical Links EPA Home > Research & Development > Exposure Research > Publications/Presentations > End Hierarchical Links

 

A Pilot Study of the Influence of Residential Hac Duty Cycle on Indoor Air Quality

spacer
spacer
Abstract: A simple methodology was developed to collect measurements of duty cycle, the fraction of time the heating and air conditioning (HAC) system was operating inside residences. The primary purpose of the measurements was to assess whether the HAC duty cycle was related to reductions in indoor particulate matter (PM) concentrations. A miniature temperature logger placed on an HAC outlet vent monitored changes in temperature as the system cooled or heated the residence. Temperature step changes signaling duty cycle periods were identified using spreadsheet macros. Parallel measurements of 24-hour integrated air exchange rates (AERs) and indoor PM2.5 and PM10 concentrations were collected to determine relationships with the duty cycle. The mild temperatures (mean = 18.7 degrees C) present during the Spring season of the RTP PM Panel Study and personal comfort preferences caused low and variable daily duty cycles (mean = 0.061, std. dev. = 0.054) in both heating and cooling mode. Warmer ambient temperatures during the Fall season of the Tampa Asthmatic Children Study (TACS) resulted in cooling-only HAC operation, with a higher mean duty cycle of 0.21 (std. dev. = 0.11). Statistically significant linear relationships were observed between daily average duty cycle and the ambient temperature for both studies. Duty cycle exhibited a strong diurnal pattern commensurate with ambient temperature fluctuations. Duty cycles were positively associated with the residence AERs for heating-mode operations, but negatively associated when operating in cooling mode. Personal preferences contributed to the variability in the relationship between duty cycle and air exchange rate. The relationship between duty cycle and PM2.5 or PM10 indoor-outdoor ratios were not statistically significant. The association of duty cycle with indoor-outdoor ratio was confounded by the short time span (mean of 10.3 minutes for the TACS) of HAC system operation and the presence of strong indoor sources altering the indoor concentration levels.

This research was sponsored by U.S. EPA contract 68-D-99-012 to RTI International. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute an endorsement or recommendation for use.
spacer
Citation:Thornburg, J., C. Rodes, P. A. Lawless, C. Stevens, and R. W. Williams. A Pilot Study of the Influence of Residential Hac Duty Cycle on Indoor Air Quality. Presented at AWMA Particulate Matter Indoor Air Quality and Envineering Solutions Symposium, Research Triangle Park, NC, July 21, 2003EPA/600/A-03/177 (NTIS PB2004-100891).
spacer
spacer
Contact: Liz Hope - (919) 541-2785 or hope.elizabeth@epa.gov
spacer
Division: Human Exposure & Atmospheric Sciences Division
spacer
Branch: Exposure Measurements & Analysis Branch
spacer
Product Type: Sympos/Conf
spacer
Presented: 07/21/2003
spacer
Related Entries:
spacer
Bullet Item Outdoor Vs. Human Exposure: NERL PM Exposure Panel Studies
spacer Relationship Reason:   A Project of the Product
spacer
spacer
spacer

 

ORD Home | Search EPA | Search NERL | Search EIMS | Contacts | Help

 
Begin Site Footer

EPA Home | Privacy and Security Notice | Contact Us

Last Updated on Monday, October 22, 2007
URL: http://cfpub.epa.gov