A novel electrostatic precipitator-type small air purifier with a carbon fiber ionizer and an activated carbon fiber filter

We developed and investigated the air cleaning performance of a novel electrostatic precipitator (ESP)-type small air purifier with a carbon brush ionizer and an activated carbon fiber (ACF) filter. This version had a high particle charging rate and a low ozone emission rate. Applying a negative voltage of 10 kV to the carbon brush ionizer increased the single-pass particle collection efficiency of 0.3-μm particles from 17.8% to 47.1%. The flow rate was maintained at 362 L/min, and the efficiency increased to 64.2% as we applied a negative voltage to the collection stage and increased the voltage to 10 kV. This was relatively low when compared to a market-leading commercial HEPA filter-type small air purifier (80.7%). However, our novel purifier showed a particle clean air delivery rate (CADR) of 0.31 m3/min, approximately a 1.7 times higher than that for the commercial purifier (0.18 m3/min) due to its high flow rate and low pressure drop. We measured the gas removal efficiency in a 1-m3 test chamber with acetic acid, acetaldehyde, and ammonia; after 30 min of operation, the results were 97.9%, 92.4%, and 87.8% for the novel purifier and 95.2%, 65.4%, and 57.9% for the commercial purifier, respectively. The ozone concentration was measured in a closed test chamber (30.4 m3) over 15 h of continuous operation, and it showed a maximum value of 2.5 ppb, much lower than the current standard for ESPs (50 ppb).