With a move toward smarter building ventilation systems that respond to specific inside-air conditions as they arise — resulting in healthier air at a lower cost — comes a need for more precise monitoring of indoor conditions such as temperature, humidity, carbon dioxide levels, and pollutants such as formaldehyde gas. The VOC True Read is a new technology that enables the long-sought accurate detection of formaldehyde gas in indoor air. This affordable device screens out interfering compounds that lead to false readings of indoor formaldehyde gas, allowing building systems operators to more quickly respond to precise readings of indoor formaldehyde gas, bringing in fresh air to maintain healthy standards.
The VOC True Read device, developed by former Berkeley Lab post-doctoral scholar Meera Sidheswaran and Berkeley Lab researcher Lara Gundel, uses an innovative honeycomb filter design that strips water vapor, alcohols, and other volatile organic compounds (VOCs) from a sample, allowing formaldehyde — or other target gases — to pass through to a detector. The filter presents an economical solution to the need for accurate formaldehyde measurement in that it can be attached to, and retrofit, in-place sensors to increase their detection accuracy. The filter's internal structure can be arrayed various ways to adsorb other interferents, as needed. The device provides accurate, long-term, inexpensive, real-time monitoring of building air using proton transfer-reaction mass spectrometry (PTR-MS) to assist exposure assessment and demand-controlled ventilation.
Formaldehyde, labeled a known carcinogen by the National Toxicology Program of the Department of Health and Human Services, is ubiquitous in the indoor environment of buildings in the form of gas. While higher levels of formaldehyde exposure can cause cancer, lower-level exposure can trigger nasal and eye irritation, nausea, difficult breathing, or allergic reactions and asthma attacks. Workers in office buildings are commonly exposed to varying levels of formaldehyde gas given off by products made with pressed wood containing glues made with urea-formaldehyde resin.
To mitigate pollutants such as formaldehyde from inside air, conventional building ventilation practices simply bring in a set amount of outside air, which must be conditioned before being circulated within the space. This can result in over-ventilation, wasting both energy and money. Demand-control ventilation (DCV) systems use sensors to monitor and measure the air and provide feedback to a central controller, resulting in an increase or decrease in ventilation as needed. Compared with conventional ventilation strategies, DCV results in significant energy savings of up to 40%. To make DCV more reliable, a growing market for accurate formaldehyde sensing and real-time monitoring technology has emerged.
Currently available real-time formaldehyde sensors work well in environments contaminated only with formaldehyde, but have long been plagued by a lack of accuracy and drift-prone readings in environments with interfering elements such as water vapor and polar VOCs such as methanol and ethanol — typical conditions in most indoor work environments.
As air flows freely through the inlet of the VOC True Read device, it passes through an elongated chamber (or chambers) containing tubes covered in a commercially available polymeric or carbon-based adsorbent. Low molecular weight oxygenated compounds (such as ethanol) bind easily to the adsorbent while formaldehyde, unaffected, passes through the device's outlet and on to a detection device. The surface area of the coated channels is sufficient to adsorb interfering gases. The filter is compatible with sensors and instruments ranging from microelectronic metal-oxide semiconductors to proton transfer reaction mass spectrometers (PTR-MS).
The internal design's channels can be arrayed in various ways, depending on need: as a honeycomb, open-cell foams, or multiple co-linear cylinders. A similar inlet can be added with a stripper designed to remove water vapor from the sampled air. A plurality of denuders can be used in one device, each targeting specific compounds. The VOC True Read's architecture can be tailored to remove other gases, including aromatic compounds such as toluene, benzene, o-xylene, or limonene; and alcohols and alkanes. The air sample, after passing through the filtration device, can flow on to a variety of detection devices.
This versatility also makes the device useful in industrial air-pollution monitoring in facilities where formaldehyde use is heavy (e.g., in the manufacture of paper, paint, and textiles); medical research (monitoring a patient's breath for biomarkers of disease); in mortuaries and hospitals, where formaldehyde gas levels can soar; and on microelectronic sensors.
Using this retrofit, manufacturers can market their ventilation systems as smart, accurate means for keeping air safe to breathe at much lower cost. This technology will help advance existing test sensors from a research to a marketable phase by increasing their accuracy. Some smaller formaldehyde sensors currently available can be fitted with the VOC device. The technology can also be used in medical research, such as measuring VOC content of a subject's breathing. Another potential application is the real-time monitoring of outdoor air pollution.
This technology is available for licensing.
"Channelized Filter Inlets or Strippers for Improved Real-Time Formaldehyde Measurement" (AvailableTechnologies). Berkeley Lab Technology Transfer and Intellectual Property Web site.