Use of Portable Air Purifiers in Homes: Operating Behaviour, Effect on Indoor PM₂.₅ and Perceived Indoor Air Quality

Source: Building and Environment, Volume 191, “Use of portable air purifiers in homes…” (2021) 科学直通车

Summary

This study focused on how portable home air purifiers (HAPs) affect indoor particulate matter (PM₂.₅) concentrations in actual home bedrooms, and how users perceive air quality. It also looked at how people use purifiers (operating behavior) under different indoor/outdoor conditions (open or closed windows) and what motivates them to turn the purifier on. The study was conducted in a number of homes over time. 科学直通车

Key findings:

• On average, using a portable air purifier in a bedroom reduced PM₂.₅ by ≈45% over 90 minutes. This figure held even when windows were opened part of the time, though effectiveness was higher when windows were closed. 科学直通车

• Occupants reported perceiving the air as fresher, cleaner or “cooler” when the purifier was running. The subjective perception correlated moderately with observed PM₂.₅ reductions. 科学直通车

• Interestingly, many occupants operated purifiers in response to thermal comfort or warm weather rather than pollution concerns. That is, higher outdoor temperatures or warm rooms led people to turn on purifiers, regardless of measured indoor particle levels. 科学直通车

• The study also found that window opening behavior mattered: if windows were open, outdoor particles come in, degrading the purifier’s effectiveness (or requiring more time or higher purification power). Nevertheless, even under imperfect conditions (some outdoor air infiltration), purifiers still produced measurable benefits. 科学直通车

Understanding & Analysis

I believe this study provides important real-world insight, because many lab studies don't capture how people actually behave, and how that behavior affects air purifier effectiveness.

Some reflections:

1. Real behavior matters: The fact that people often turn on purifiers for thermal comfort (e.g. to feel “cool” or because air seems stuffy or warm) rather than air quality suggests a gap in awareness. If users are more aware of particle pollution and health implications, they might operate purifiers more optimally (e.g. when outdoor smoke is bad, when windows are closed).

2. Effectiveness under non-ideal conditions: Homes are not perfect sealed chambers. Windows open, occupant actions vary. The finding that purifiers still reduce PM₂.₅ ~45% even under varying conditions is encouraging—it shows purifiers are useful even when conditions are not optimal.

3. Trade-offs and energy/time: To achieve ~45% reduction in 90 min implies significant time and continuous operation. People often turn purifiers off or reduce operational intensity (fan speed, etc.) which reduces benefit. Also, power usage and noise may dissuade continuous use.

4. Subjective perception vs measurement: That occupants reported perceivable differences is important; even if PM₂.₅ isn’t always visible, people feel better when purifiers run. That helps in adoption (if people believe it's helping, they may continue to use them). Also, it suggests that human satisfaction is a factor in design (noise levels, appearance, etc.) not just technical specs.

5. Policy and public health: Findings support promoting portable air purifiers as part of interventions during smoke or pollution events, or more generally for indoor air quality. Education campaigns to inform occupants about when and how to use purifiers (close windows, maintain filters, run high enough fan speed) could increase effectiveness.

Limitations & Next Steps

• The study was conducted in a set of homes; results may vary in different climates, building construction types, pollution levels, or with different purifier models. Generalizing requires broader studies.

• Long-term health outcomes were not measured; while reduced PM₂.₅ is good, how much health benefit accrues over time depends on exposure and vulnerability (children, elderly, asthma patients etc.).

• Filter maintenance, noise, cost, power consumption over time were not deeply analyzed; for sustained usage, these are important constraints.

• Further work could examine multi-pollutant scenarios (smoke + VOCs + pathogens) and how purifiers perform together with ventilation, filtration (HVAC), sealing, etc.

Conclusion

This research demonstrates that portable air purifiers can significantly improve indoor air quality even in everyday home settings, reducing PM₂.₅ substantially and improving occupants’ subjective comfort. It also reveals that people often do not use purifiers exactly when needed; awareness and behavioral factors are key. For designers, making purifiers that are quieter, more energy-efficient, easy to maintain, and more informative (e.g. displaying current particle level) could increase usage. For health policy, amplifying public awareness and possibly subsidies or guidance could help realize the full benefit.