A University of Texas Study confirms that some air cleaners actually increase ultrafine particles and formaldehyde.
Here is another study to confirm the ill-effects of ozone producing air cleaners in indoor environments. In an article that appeared in Atmospheric Environment earlier this year researchers at the University of Texas found that ion generators and electrostatic precipitators that produced ozone were actually initiating chemical reactions that created more particles than the machines removed. Tests also confirmed that formaldehyde was a by-product in these chemical reactions.
The paper is entitled “Ultrafine Particle Removal and Generation by Portable Air Cleaners” and the authors are Michael S. Waring, Jeffrey Siegel and Richard Corsi. Tests were conducted in a 14.75 m3 stainless steel chamber on 5 air cleaners. Two of the air cleaners were HEPA machines, one was an electrostatic precipitator and two were ion generators.
First, the air cleaners were tested for a Clean Air Delivery Rate (CADR) and it was found that the first HEPA had a CADR of 188, the second HEPA had a CADR of 188, the electrostatic precipitator had a CADR of 284, the first ion generator had a CADR of 41 and the second ion generator had a CADR of 35.
The second phase of the investigation called for the operation of the air cleaners in the presence of either a plug-in liquid or solid air freshener. These air fresheners contributed a source of terpenes in the chamber. As a result of the terpene/ozone reactions the electrostatic precipitator and both ion generators acted as net particle generators in the range of particles between 4.61 nm and 157 nm. Formaldehyde levels were also tested with one of the ion generators in the presence of the air freshener. Substantial increases in formaldehyde were detected.
Here is the really interesting part of the study. These increases in particles and formaldehyde were created with relatively low ozone levels. The electrostatic precipitator produced 3.8 mg/hr of ozone while the ion generators produced 3.3 mg/hr and 4.3 mg/hr respectively of ozone. This sheds some additional light on the adequacy of the 50 ppb limits set by the new California law on air cleaners, the FDA limits for medical devices and the current proposal being reviewed by the CPSC. As we have contended in other articles, this 50 ppb limit is not adequate to protect consumers from the negative effects of ozone initiated indoor air chemistry.