In TEOM measurements, which statement about humidity and temperature is correct?

• A. TEOM uses heated filters; high temperature can cause loss of volatile components and humidity can affect mass readings; corrections or alternative methods may be needed
• B. TEOM uses unheated filters
• C. Humidity has no effect
• D. Temperature does not affect TEOM

Answer: (A)

In TEOM measurements, the mass of collected particulates is inferred from how a filter attached to a tapered-element oscillator changes its oscillation frequency as mass builds up. That filter is heated to keep the sample dry and reduce moisture effects during sampling. But this heating also means semi-volatile components can evaporate from the collected material, especially organic compounds, which can cause the measured mass to be lower than the true mass. Humidity adds another layer: water vapor can be taken up by the filter or by particles, changing the mass reading, and the balance between volatile organics and condensable water can shift with humidity and temperature. Because these factors can bias the results, corrections or alternative methods are often needed to account for the volatilization and humidity effects and to better reflect the actual ambient particulate mass.