Sampling methods and residential factors affecting formaldehyde concentration in indoor air

Area of Science:

• Environmental Science
• Public Health
• Indoor Air Quality

Background:

• Formaldehyde (HCHO) is a major indoor air pollutant with significant health implications.
• Residential HCHO levels are typically assessed using either short-term closed-room sampling or long-term ambient sampling.
• Understanding the discrepancy between these methods is crucial for accurate risk assessment.

Purpose of the Study:

• To compare formaldehyde concentrations measured by 30-minute closed-room sampling and 24-hour passive sampling in residential environments.
• To determine the impact of occupant behavior, such as window opening, on measured formaldehyde levels.
• To recommend the most effective sampling method for evaluating residential formaldehyde exposure.

Main Methods:

• Fifty-eight residential rooms were monitored using active sampling for 30 minutes after a minimum of 5 hours of window closure.
• Passive sampling was conducted over 24 hours, reflecting typical daily routines.
• Formaldehyde concentrations were measured in parts per million (ppm) and compared against established guidelines.

Main Results:

• The 30-minute closed-room sampling yielded a mean HCHO concentration of 0.118 ppm, with 62% of rooms exceeding the Japanese guideline of 0.08 ppm.
• The 24-hour sampling resulted in a lower mean HCHO concentration of 0.053 ppm, with only 22% of rooms exceeding the guideline.
• A linear relationship was observed between the two methods, but 24-hour levels were reduced by window opening, indicating active mitigation by occupants.

Conclusions:

• Short-term, closed-room formaldehyde measurements provide a more accurate representation of potential peak exposure levels.
• Occupant behavior, particularly ventilation practices, significantly reduces average formaldehyde concentrations over longer periods.
• For effective residential formaldehyde risk assessment, particularly considering irritation and sensitization effects, closed-room sampling is the recommended method.