Development of a portable continuous formaldehyde monitor for field and indoor use

摘要

A sensitive continuous monitro for formaldehyde (HCHO) in air has been modified to reduce its size and improve its characteristics for portable, reliable field monitoring. The monitor is suitable for HCHO monitoring in outdoor and indoor air in offices, residences and workplaces. The monitor collects HCHO into a small aqueous flow, then forms and continuously detects a fluorescent derivative in 1:1 stoichiometry with HCHO. The monitor is specific for HCHO, has a dtection limit of 0.1 ppbu, a linear range from 0.1 ppbv to at least 2 ppm, and a response time of about one minute. The monitor has been packaged into a 48 cm instrument chassis about 20 cm high, and weighing ablout 15 kg. One feature of the new package is the use of a novel non-peristaltic liquid pumping system that provides highly stable flows, and eliminates the need to change pump tubing. A coated denuder tube is incorporated in the monitor for zeroing. Except for connection to electrical power, the monitor is totally self-contained, and can operate without attention for up to three days. Operation for longer periods requires only refilling liquid reagent reservoirs in the instrument and emptying the waste reservoir. The performance of the monitor is exemplified by continuous ambient HCHO data from an industrial location near Cagliari, in Sardinia, which show ambient levels typically up to about 2 ppbv, with episodes of HCHO over 4 ppbv resulting from local sources.