Air filters may add more dangerous chemicals: study

Air filters, used to clean the air more efficiently, may be involuntarily introducing chemicals more dangerous than the ones they scrub from your house, a new study has warned.
Researchers at the Concordia University in Canada have found that a type of air filter called photocatalytic oxidation (PCO), a product already on the market, releases the chemical by-product formaldehyde, a known human carcinogen.
Doctoral graduate Lexuan Zhong and her supervisor Fariborz Haghighat present the findings of their independent testing of the PCO systems, which filter air using ultraviolet light.
This is the first time the systems have been independently tested, researchers said.

"We were shocked that some of the gases to come through the system are more dangerous than the original gas," said Haghighat, a professor with the Department of Building, Civil and Environmental Engineering.
The battle against chemical contaminants is a challenge because gases come from so many sources - carpets, paint, treated wood.

And then there are all the perfumed products we use individually, researchers said.
"Sometimes the concentration of gases inside the building is almost ten times more than outside," said Haghighat.
While regulations limit percentages of chemicals in the air, there are fewer governing specific technologies.
"Because it's new technology and the public accepts whatever the industry says, if a company says it is working they believe it.

"But it has not been tested by a standards organisation. Usually that takes time, 10 to 15 years," he said.
Besides developing systems that adequately filter without adding by-products, the other major goal is to reduce energy consumption, researchers said.
While the main (PCO) system currently in use employs mechanical ventilation, where fresh air is pumped in from outside and taken out from inside, the method is not very energy efficient.
Haghighat's colleague Chang-Seo Lee pointed to activated charcoal carbon filters (which do have standards attached) as an example of a good technology but one that requires a lot more energy to operate.

In terms of next steps for the investigation of PCO filtration, Lee said the lab wants to experiment with new versions of the technology.
"We want to develop our own catalyst because we've found the commercial catalyst does not have good efficiency," she said.
The research was published in the journal Building and Environment.