Outgassing from a material can often be hastened by heating the material. As an example, a baked-enamel finish is often tolerable for sensitive people, whereas a conventional enamel paint might take many months to outgas by itself. A few years ago, the idea of heating materials to hasten outgassing was applied to entire buildings. This is called a bake-out. Initial results of bake-outs seemed to indicate that they could be useful in reducing VOC concentrations—but the procedure occasionally damaged parts of the building. For example, in one commercial building, the concrete floor slabs moved slightly causing carpet and vinyl flooring to buckle, a window cracked, and some wood doors warped.
We do not strictly control Google ad content. If you believe any Google ad is inappropriate, please email us directly here.
A bake-out involves warming up the interior of a building with the furnace, for at least 48 hours, to an above-normal temperature (at least 95°F) and simultaneously ventilating the building at a higher-than-normal rate. This is easiest to do when indoor and outdoor temperatures are similar. In the middle of winter a furnace may be operating at capacity, and not be able to raise the temperature that much.
After some initial positive results, as researchers started investigating bake-outs more thoroughly, they encountered some unforeseen problems. For example, because it’s difficult to heat up an entire building uniformly (it takes longer to heat up a concrete floor slab than carpeting) there will be some surfaces where temperatures are lower than the air temperature. Moisture from the air, and some volatile gases, can condense on these cooler surfaces. In one 3-day, 90°F bake-out, alcohols, oxygenated compounds, and chlorinated chemicals were found in water that had condensed during the bake-out. Researchers also found that some chemicals were released into the air that aren’t released at normal room temperatures, and that the post-bake-out outgassing rates were hardly lower than the pre-bake emissions. Bake-outs seem to have little effect on formaldehyde levels in a building, probably because formaldehyde-containing materials, such as particle board, are thick enough to have a substantial reservoir of formaldehyde in them. It’s been suggested that part of the reduction in emissions that has been seen is due to the drying of concrete during a bake-out. This results in a lower relative humidity indoors, and lower outgassing rates.
The results of bake-outs are, at best, mixed. In fact, the concentrations of some compounds are higher after a bake-out, while others are lower. For thick materials, such as particle board, bake-outs have little long-term effect. Probably the best use of a bake-out is in a controlled setting by a manufacturer. In this way, a procedure can be tailored specifically to reducing emissions in one particular product. This is already being done successfully with baked-on paints.
HHI Error Correction Policy
HHI is committed to accuracy of content and correcting information that is incomplete or inaccurate. With our broad scope of coverage of healthful indoor environments, and desire to rapidly publish info to benefit the community, mistakes are inevitable. HHI has established an error correction policy to welcome corrections or enhancements to our information. Please help us improve the quality of our content by contacting allen@healthyhouseinstitute.com with corrections or suggestions for improvement. Each contact will receive a respectful reply.
The Healthy House Institute (HHI), a for-profit educational LLC, provides the information on HealthyHouseInstitute.com as a free service to the public. The intent is to disseminate accurate, verified and science-based information on creating healthy home environments.
While an effort is made to ensure the quality of the content and credibility of sources listed on this site, HHI provides no warranty - expressed or implied - and assumes no legal liability for the accuracy, completeness, or usefulness of any information, product or process disclosed on or in conjunction with the site. The views and opinions of the authors or originators expressed herein do not necessarily state or reflect those of HHI: its principals, executives, Board members, advisors or affiliates.
