This blog post, originally shared in the Pharos Signal, includes information about parts of Pharos that are no longer available. Please use it for historical reference and for the other useful information it contains.
A few months back we took a look at so-called “self-cleaning” products: products that manufacturers promise will deliver air-purifying capabilities in addition to their primary function in construction. We initially focused on products using the photocatalysis of titanium dioxide to convert nitrogen oxide air pollutants into various breakdown products that could be washed away with the rain or a garden hose.
Since then, readers have asked us to look into another line of products marketed as air-purifying – hungry building products that utilize chemical “scavengers” to gobble up indoor air contaminants like formaldehyde. Are hungry building products healthy building products?
Scavengers are chemicals and materials added to existing product formulations for the purpose of chemically reacting with a targeted trace ingredient.  This technology was originally developed for use in particleboards held together with formaldehyde-based binders. Manufacturers added scavengers to the binder so they could chemically bond with any formaldehyde that would be released from the boards over time.* [2, 3] However, a recent review of these treated boards found that they may re-emit the formaldehyde they sequester when subjected to high temperatures or high humidity.  This limitation of scavengers could have real-world consequences; if for example, these boards were installed in an office building in the hot, humid American Southeast, the air conditioner turned off to save energy over the weekend. Office workers could return to their desks Monday morning and be exposed to large doses of re-emitted formaldehyde.
The use of scavengers has since expanded from particleboard to other product types – insulations, wet-applied coatings, and drywall to name a few. We wondered: if the same scavengers developed for particleboard were being used in other building materials, were these new products also capable of re-emitting the formaldehyde they absorb? To answer that question, we started with one of the most heavily marketed scavenger products available: AirRenew gypsum wallboard made by CertainTeed.
The scavenger technology used in the AirRenew boards is proprietary, but CertainTeed representatives have described it is “a chemical formaldehyde scavenger, similar to those sometimes added to wood products to decrease formaldehyde offgassing.”  But, unlike particleboard, CertainTeed claims that the scavengers used in AirRenew convert formaldehyde found in ambient air into a new (and also proprietary) compound, which is then stored permanently within the core of the boards. [6, 7]
When presented with the apparent limitations of scavenger additives in particleboard, our contact at CertainTeed reported that formaldehyde releases have not been detected when AirRenew is being recycled, a process that requires high temperatures  (and presumably high humidity since gypsum boards start their life as a wet slurry).
In addition to CertainTeed’s assurances that formaldehyde is not re-remitted once absorbed, AirRenew does carry GreenGuard certifications and a UL validation that the boards are capable of “permanent formaldehyde absorption capacity of .4g/m2 of surface area.” But, these third party evaluations don’t necessarily put concerns about scavengers potentially re-emitting formaldehyde in the future to rest.
GreenGuard certification programs are intended to recognize products with low VOCs by measuring their emissions during the first two weeks after leaving the factory. This is a good predictor of how ingredients added to a product in the factory will contribute to indoor emissions over time, but does not assess whether formaldehyde a product absorbed after installation might be released at a later date. 
Moreover, the UL validation of permanent absorption is based on testing protocols that do not include conditions of high temperature or humidity. 
As we noted in our first look at “self-cleaning” products, these hungry building products could play an important role in creating a truly regenerative material economy. They could also end up being just another form of greenwash. While AirRenew certainly seems to be a promising application of formaldehyde scavengers, greater transparency and more research into on-site performance is needed, leaving us with lots of questions about these products. We encourage CertainTeed to disclose more about their additives, and about the compound formaldehyde is converted into before being absorbed by the boards.
We look forward to someday seeing AirRenew in the Pharos Building Products Library.
* Kim et al identifies a variety of chemical compounds as formaldehyde scavengers, including urea, ammonia chloride, organic amines, paraffins, catechin, vanillin, tannins, and wheat flour.
Thanks to Susan Sabella, Bill Walsh, Jim Vallette, Sarah Lott and Tom Lent for their great discussions on this topic and contributions to this post.
Melissa Coffin, Data Systems Project Leader, is responsible for leading the development of the Pharos Project's Building Products Library. Follow Melissa on Twitter: @HBNmelissa
 “Definition of a Scavenger.“ www.Chemicool.com Available http://www.chemicool.com/definition/scavenger.html; accessed 23 Sep 2013.
 Salthammer T, Mentese S, and Marutzky R. “Formaldehyde in the Indoor Environment.” Chemical Reviews vol 110, no 4: 2536–2572. Available http://pubs.acs.org/doi/abs/10.1021/cr800399g. Accessed Sep 17 2013.
 Kim S, Kim H-J, Kim H-S, and Lee H. “Effect of Bio-Scavengers on the Curing Behavior and Bonding Properties of Melamine-Formaldehyde Resins.” Macromolecular Materials and Engineering vol 291: 1027-1034. Available http://onlinelibrary.wiley.com/doi/10.1002/mame.200600213/abstract. Accessed Sep 17 2013.
 Frihart C, Wescott J, Chaffee T, and Gonner, K. “Formaldehyde Emissions from Urea- Formaldehyde– and No-Added- Formaldehyde–Bonded Particleboard as Influenced by Temperature and Relative Humidity.” Forest Products Journal vol 62, no 7/8: 551-558. Available http://184.108.40.206/documnts/pdf2012/fpl_2012_frihart001.pdf, accessed 18 Sep 2013.
 Melton P and Wilson A. “Air Renew Wallboard Absorbs Formaldehyde from Indoor Air,” Environmental Building News. 1 Mar 2011. Available http://www.buildinggreen.com/auth/article.cfm/2011/2/28/Air-Renew-Wallboard-Absorbs-Formaldehyde-from-Indoor-Air/. Accessed 18 Sep 2013.
6] CertainTeed Gypsum, Inc. “AirRenew Indoor Air Quality Board” brochure. 2011. Available http://www.certainteed.com/resources/Gyp_AirRenew.pdf/ Accessed Sep 16 2013.
 CertainTeed. Email correspondence. 7 Oct 2013.
 UL. “GREENGUARD Certification Program Method for Measuring and Evaluating Chemical Emissions From Building Materials, Finishes and Furnishings.” Document no. 2821, 2 Apr 2013.
 Underwriter Laboratories. Telephone interview. 23 Sep. 2013.