Indoor Air Quality Risk Perception Study and Modeling Analysis of Factors that Affect Indoor Occupant Exposure

Abstract

People spend the majority of their time in indoor environments where pollutant concentrations can be 70 to 100 times greater than those found outdoors. Elevated indoor concentrations pose serious health risks to the occupants of buildings. This research included designing, distributing, and analyzing the results of an indoor air quality risk perception survey to assess the state of knowledge on indoor air risks of residents in North Carolina. This research also included a modeling application that assessed some of the factors that affect indoor occupant exposure including occupancy cycles, particle removal efficiency of air cleaners, air exchange rate of air cleaners, and building characteristics. The RISK software developed by the EPA Indoor Environmental Management Branch was utilized for the modeling application.

Results from the survey indicated that respondents were more knowledgeable of specific risks than others. Respondents cited mold (99%), inadequate ventilation (92%), and cigarette smoke (91%) as the greatest contributors to poor indoor air quality. Many respondents (71%) were willing-to-pay up to $30/month for indoor air quality treatment. Respondents showed uncertainty towards the topic of air cleaners that use ozone and over 50% of respondents agreed that the risks involving poor indoor air quality can be more effectively communicated. Information obtained from write-in questions determined that 16 respondents sought more information on how to select an air cleaner for their home. Overall, respondents expressed their concern for indoor air quality risks and it was determined that the specific topic of how to select an appropriate air cleaner for a residence can be more effectively communicated to the public by environmental professionals.

Results from the modeling analysis of factors affecting occupant exposure showed that differing the air cleaner air exchange rate from 1 to 6.75 resulted in exposure reductions that had an average change of -36.4%. Varying particle removal efficiency by 50 percentage points resulted in exposure reductions that had an average change of -9%. Thus, air exchange rate was found to be the more sensitive variable. Occupancy cycles and building characteristics were shown to affect occupant exposure as well. Occupants who were simulated to spend longer time periods in the same room as the cleaner tended to receive slightly higher overall exposure reductions. Thus, placement of an air cleaner in a room that all occupants visit during the day may maximize total occupant exposure reductions. The size of the sink area in a particular room relative to the volume of the room affects exposure. The model results imply that small rooms with small sink areas resulted in higher occupant exposures than larger rooms having larger sink areas.

The survey and modeling results were utilized to draft a list of indoor air quality risk communication priorities and recommendations for effective communication. Key recommendations include establishing a set of safe levels or guidelines for potential indoor contaminants and increased communication between environmental professionals and the media in an effort to raise awareness and educate the public on all aspects of indoor air quality issues.