Available Technology

Channelized Filter Inlets or Strippers for Improved Real-Time Formaldehyde Measurement IB-3035

Berkeley Lab researchers Lara Gundel and Meera Sidheswaran have developed an innovative filter design that efficiently strips water vapor, alcohols, and other volatile organic compounds (VOCs) from airstreams to be sampled for concentrations of formaldehyde. The efficient design makes real-time, long term gas concentration monitoring practical. The Berkeley Lab design resembles an elongated honeycomb that quickly strips VOCs from the airstream as it freely passes through. The cells of the honeycomb are tubes coated with commercially available polymeric or carbon-based adsorbents to which low-molecular weight oxygenated compounds (such as ethanol) easily bind, while formaldehyde passes through unhindered. The coated channels provide sufficient surface area to adsorb interfering gases quickly and efficiently, so the air sample can then be delivered to the inlet of a detection device. The filter will work with commercially available sensors and instruments ranging from microelectronic metal-oxide semiconductors (MOS) to highly sensitive Proton Transfer Reaction-Mass Spectrometers (PTR-MS). Crucial to the inlet or stripper design is the coated-channel architecture, which can be arrayed in the honeycomb cluster, open-celled foams, or multiple co-linear cylinders. The organic chemical stripper system can be readily paired with a similar inlet or stripper designed to remove water vapor, which is also known to confound VOC test results. The system architecture is programmable; channels can be custom-coated to adsorb different chemicals for different applications. This is a critical feature for Demand Controlled Ventilation (DCV) systems. Just as a room thermostat uses air temperature readings to govern use of heating or cooling equipment, an intelligent DCV system would use readouts from accurate VOC sensors to determine whether energy-intensive air purification modules should be switched on or off. It is estimated that efficiently operated DCV systems could yield energy savings of 10-40%. Accurate measurement of formaldehyde levels is essential because the chemical is both a common indoor air pollutant and a carcinogen. However, standard airstream tests are notoriously unreliable because water vapor and common VOCs such as ethanol or methanol interfere with precise measurement of formaldehyde levels. Complex filtering systems to remove these interferents from an air sample currently require high power stripping systems that make real-time, long-term testing impractical. The Berkeley Lab technology’s applications are not limited to the monitoring of indoor air-pollution. The selective stripping system can also be used in medical settings to measure, from a patient’s breath, real-time levels of VOC components, which are being evaluated as biomarkers for conditions such as chronic obstructive pulmonary disease.
Benefits: 
Compact and portable - Improves real time formaldehyde measurement accuracy - Scalable - Adaptable for removal of different gas-specific interferents
applications: 
Internal Laboratory Ref #: 
IB-3035
Patent Status: 
Patent pending. Available for licensing or collaborative research.
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