Detection of formaldehyde using off - axis integrated cavity output spectroscopy with an interband cascade laser

A continuous-wave, mid-infrared, distributed feedback , interband cascade laser was used to detect and quantify formaldehyde (H 2 CO) using off-axis, integrated cavity output spectroscopy in gas mixtures containing ≈ 1–25 parts in 10 6 by volume (ppmV) of H 2 CO. Analysis of the spectral measurements indicates that a H 2 CO concentration of 150 parts in 10 9 by volume (ppbV) would produce a spectrum with a signal to noise ratio of 3 for a data acquisition time of 3 s. This is a relevant sensitivity level for formaldehyde monitoring of indoor air, occupational settings, and on board spacecraft in long duration missions in particular as the detection sensitivity improves with the square root of the data acquisition time. 1 Introduction 1.1 Formaldehyde and its detection Formaldehyde (H 2 CO) is widely used in the manufacture of building materials and numerous household products. Out gassing of formaldehyde from these materials may lead to elevated indoor air levels particularly for poorly ventilated structures. It is also an important intermediate in the oxidation of hydrocarbons in both combustion systems and in the troposphere. Thus, H 2 CO may be present in substantial concentrations in both indoor and outdoor air samples. Tropospheric H 2 CO concentration measurements provide a means of validating photochemical model predictions that play a key role in our understanding of tropospheric ozone formation chemistry [1]. Formaldehyde is a pungent-smelling, colorless gas that causes a variety of effects (including watery and/or burning eyes, nausea, and difficulty in breathing) in some humans exposed to H 2 CO levels of only 100 ppbV. Known to cause cancer in animals, it is also a suspected human carcinogen. Formaldehyde is detected by odor by humans ranging from concentrations of 0.07 to 1.2 ppmV in air. The Occupational Safety and Health Administration has established permissible exposure limit (PEL) of 0.75 ppmV averaged for an eight-hour work day and short term exposure limit (STEL) of 2 ppmV averaged over 15 min [2]. At levels ten times the PEL, respiratory protection is required. Other organizations have taken a more conservative approach to formaldehyde management. For example, the threshold limit value (TLV) for H 2 CO established by the American Conference of Governmental Industrial Hygienists is 0.3 ppmV as a " ceiling limit " not to be exceeded at any time, and has classified it as a " suspected human carcinogen ". A committee of the …