Formaldehyde is volatile, widely used, and linked to numerous health problems. As such, it is a significant indoor air pollutant – but being able to measure formaldehyde concentrations accurately and easily has long proven difficult due to issues with cross-sensitivity in detectors. In this article, we look at the dangers surrounding formaldehyde and see how the SFA30 formaldehyde sensor provides a new level of selectivity in formaldehyde detection.
Formaldehyde 101
While known to most as a biology-class preservative or embalming agent, formaldehyde is actually one of the most important basic industrial chemicals in the world. In fact, it’s estimated that around 18 million tons of formaldehyde are produced worldwide each year.1
Formaldehyde is a hugely versatile and important chemical precursor, and it’s used in the manufacture of thousands, if not millions, of industrial and consumer products. The greatest quantity of formaldehyde is used in the production of resins, which have a long list of applications.
Primarily, formaldehyde resins are used to manufacture particle boards, plywood and furniture. They are also used in the production of curable plastics, surface coatings, and controlled-release nitrogen fertilizers and serve as auxiliaries in the textile, leather, rubber, and cement industries. Formaldehyde is so uniquely useful in these applications that it can seldom, if ever, be replaced by other compounds.
A dangerous air pollutant
Concern over formaldehyde as a dangerous air pollutant began in the 1960s when inhabitants of prefabricated houses started to report adverse health effects, including irritation of the eyes and airways.2 It was soon determined that formaldehyde emissions from particleboards bonded with formaldehyde resins were to blame.
Although formaldehyde occurs naturally in the body, exposure to formaldehyde in the air can be dangerous. Exposure to concentrations in excess of 0.1 ppm can cause irritation to the eyes and airways, and chronic exposure is linked to a range of health conditions, including asthma and cancer.
Formaldehyde is classified by the CDC as a systemic poison, while safety and occupational health authorities worldwide have defined permissible exposure levels for formaldehyde both in occupational and non-occupational environments.3,4
Part of the problem is that formaldehyde is a gas at room temperature. This means that small amounts of free formaldehyde present in resins are prone to evaporate into the surrounding air, where they can potentially reach harmful concentrations. Due to the ubiquity of formaldehyde in building materials and consumer products, this is especially problematic indoors, with wood-based materials, flooring, insulation materials and coatings representing a particular hazard.
There are a few strategies for mitigating the risk of dangerous exposure to formaldehyde. Of course, the best approach is to eliminate sources before they pose a risk: for example, some organizations encourage the use of low-emitting materials in buildings.5
Of course, removing formaldehyde sources is not always practical when so many common materials and products contain the compound. Where sources already exist, simple ventilation measures can be extremely effective at decreasing levels of formaldehyde (and other air pollutants): this could involve installing ventilation systems in industrial environments or simply opening windows. However, as with any gas hazard, the only way to truly ensure safety is by using equipment that can detect and quantify formaldehyde concentrations in the air.
Formaldehyde sensing
The World Health Organization suggests an exposure limit of 0.08 ppm to prevent sensory irritation and other health problems.6 But the development of usable sensors capable of detecting formaldehyde concentrations in this range has not been straightforward.
One of the primary challenges facing formaldehyde detectors is selectivity: sensors geared toward the detection of formaldehyde are typically also sensitive to other VOCs, which commonly occur at much higher concentrations in indoor environments.
The accuracy with which formaldehyde can be detected takes a hit outside the lab, due in no small part to the huge variety of VOCs in typical indoor environments. Many of these VOCs, present in ppm concentrations, can fool formaldehyde sensors into registering higher levels of formaldehyde than are actually present in the air.
For a long time, only spectroscopic devices have reliably achieved accurate measurements of formaldehyde at concentrations of interest – however, these devices are typically complex, expensive and difficult to transport; rendering them unsuitable for most monitoring applications.
The SFA30 Formaldehyde sensor from Sensirion
The SFA30 is an electrochemical formaldehyde sensor developed specifically to fulfill the need for accurate, fast and simple formaldehyde detection in all environments.7 Engineered for formaldehyde selectivity, the sensor offers extremely low cross-sensitivity to other VOCs (less than <0.2% for ethanol).
Importantly, the SFA30 has a unique level of accuracy when exposed to other volatile organic compounds (VOCs), which are omnipresent in most domestic and workplace environments, eliminating false positives and extending the sensor’s lifetime. Notably, the SFA30 has a low cross-sensitivity to ethanol, which produces inaccuracies in comparable sensors.
Developed to operate in any environment, the SFA30 contains an integrated humidity sensor and thermometer, enabling a specially-developed algorithm to compensate for the effects of moisture and temperature on the sensing element. The SFA30 features anti-dry technology to ensure the longevity of the liquid electrolyte and ensure long-lasting stability over a six-year lifetime. Versatile mounting options along with selectable digital UART and I2C interfaces mean the SFA30 can be easily integrated into devices such as air purifiers, air conditioners, and indoor air quality monitors.
Sensirion is an industry leader in environmental sensor technology. To find out more about the capabilities of the SFA30 or our other sensors (including particulate, VOC and CO2), get in touch with us today.
References and further reading
1. Franz, A. W. et al. Formaldehyde. in Ullmann’s Encyclopedia of Industrial Chemistry (ed. Wiley-VCH Verlag GmbH & Co. KGaA) 1–34 (Wiley-VCH Verlag GmbH & Co. KGaA, 2016). doi:10.1002/14356007.a11_619.pub2.
2. Salthammer, T., Mentese, S. & Marutzky, R. Formaldehyde in the Indoor Environment | Chemical Reviews. https://pubs.acs.org/doi/10.1021/cr800399g.
3. Formaldehyde | Medical Management Guidelines | Toxic Substance Portal | ATSDR. https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=216&toxid=39.
4. Formaldehyde - Overview | Occupational Safety and Health Administration. https://www.osha.gov/formaldehyde.
5. US EPA, O. ANSI/ASHRAE/USGBC/IES Standard 189.1-2014: Standard for the Design of High-Performance Green Buildings Except Low-Rise Residential Buildings (ASHRAE 189.1). https://www.epa.gov/smartgrowth/ansiashraeusgbcies-standard-1891-2014-standard-design-high-performance-green-buildings (2014).
6. Kaden, D. A., Mandin, C., Nielsen, G. D. & Wolkoff, P. Formaldehyde. WHO Guidelines for Indoor Air Quality: Selected Pollutants (World Health Organization, 2010).
7. SFA30 Formaldehyde Sensor Module | Sensirion. https://www.sensirion.com/en/environmental-sensors/formaldehyde-sensor-sfa30/.
