Development of a novel hand-held formaldehyde gas sensor for the rapid detection of sick building syndrome

The majority of conventional sensors for monitoring formaldehyde (HCHO) in air have several drawbacks, in terms of sensitivity, selectivity. and sampling time. In this report, a novel hand-held HCHO gas sensor for the sick building syndrome (SBS) prevention and control is developed with a significantly short sampling time. A well-described reagent, 4-amino hydrazine-5-mercapto-1,2,4-triazole (AHMT) was utilized in the development of the novel gas sensor. AHMT of 100 mu 1 and potassium hydroxide solution were dropped on a circular filter by using a specially developed hanging drop kit. When the filter was exposed to HCHO gas at the rate of 400 ml/min, AHMT reagent on the filter reacted with HCHO to produce a change in its color. The color change was recorded by measuring the intensity of reflected light using a photodiode, which was illuminated by an LED at 540 nm. The response was defined as % of the voltage drop. The filter color intensity increased with sampling time in a concentration range of 0.04-1 ppm HCHO, and also the filter gave no response in the absence of HCHO. The limit-of-detection (LOD) of 0.04 ppm HCHO within a sampling time of 3 min was achieved. Thus, this method could be used to detect HCHO at the WHO standards (0.08 ppm) within 3 min. Moreover, our device did not respond to other SBS causing reagents, such as other aldehydes and volatile organic compounds. In conclusion, we have developed a rapid, selective and simple HCHO gas sensor for SBS, which is also a suitable device for on-field operations. (c) 2004 Elsevier B.V. All rights reserved.