An automatic monitor of formaldehyde in air by a monitoring tape method

Abstract

An automatic monitor has been developed for measuring formaldehyde in air using a sensitive tape for formaldehyde. It is based on the color change of the tape on reaction with formaldehyde. The porous cellulose tape, containing silica gel as an absorbent and impregnated with the processing solution containing hydroxylamine sulfate, Methyl Yellow (pH indicator; pH 2.9-4.0, red-yellow), glycerin and methanol, was found to be a highly sensitive means of detecting formaldehyde and maintains a stable sensitivity. When the tape was exposed to a sample of air containing formaldehyde, the color of the tape changed from yellow to red. The degree of color change was proportional to the concentration of formaldehyde at a constant sampling time and flow rate, and it could be recorded by measuring the intensity of reflected light (555 nm). The tape could be used to detect down to 0.08 ppm (World Health Organization standard) of formaldehyde with a sampling time of 30 min and a flow rate of 100 mL min-1. Reproducibility tests showed that the relative standard deviation of response (n = 10) was 3.8% for 0.1 ppm formaldehyde. The monitor is simple, specific, capable of unattended operation and is recommended for both laboratory and field operation.

Silicon-based micro-gas sensors for detecting formaldehyde

“…Formaldehyde (CHOH) is one of the harmful VOC gases, coming from building materials, interior decoration materials, wood furniture, carpet, and so on. Formaldehyde gas strongly irritates human eyes and nose, and is a kind of carcinogen [1][2][3][4][5][6]. Many kinds of VOCs are harmful even at very low concentration.…”

Selective Detection of Formaldehyde Gas Using a Cd-Doped TiO2-SnO2 Sensor

“…The conventional method used for monitoring indoor VOCs is generally time-consuming and expensive because it involves on-site sampling of indoor air but ensuing analysis of the sampled air in a laboratory [2–5]. To date, there are still no electronic sensors available for in situ detection of indoor VOCs, in particular, the formaldehyde [6], which has already been classified as a probable carcinogen [7–9]. For this reason, extensive research has been conducted on developing a sensor that has a simple device structure and can be put into practical use.…”

A Colorimetric Chemical Sensing Platform for Real-Time Monitoring of Indoor Formaldehyde

“…With this method, a response time of 2 minutes has been achieved in our sensing platform, as shown in Fig. 2(d), which is much less than most colorimetric formaldehyde sensors [13]- [15]. + 1 min sampling).…”

“…Compared to PID and electrochemical sensors, the colorimetric sensors are more selective because they utilize a specific chemical reaction of formaldehyde with carefully selected chemical sensing materials. However, these colorimetric sensors suffer from major drawbacks, including slow response (typically 30 minutes), high detection limit, and low humidity tolerance [13]- [16].…”