Concordia University Researchers Reveal Major Air Filter Defect

In search of a healthy and energy efficient building

Concordia University, July 15, 2015. Image credit: Fariborz Haghighat

Imagine if, in an effort to clean the air more efficiently, you were involuntarily introducing chemicals more dangerous than the ones you were trying to scrub. Concordia University researchers have found that this exact situation is happening with a type of air filter called photocatalytic oxidation (PCO), a product already on the market. The chemical by-product? Formaldehyde, a known human carcinogen.

In a paper published in the journal Building and Environment, recent doctoral graduate Lexuan Zhong and her supervisor Fariborz Haghighat present the findings of their independent testing of the PCO systems, which filter using ultraviolet light. This is the first time the systems have been independently tested.

Besides developing systems that adequately filter without adding by-products, the other major goal is to reduce energy consumption. 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. Neither are some other modern systems: Haghighat’s colleague Chang-Seo Lee points 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.

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