Two new methods for real-time measurement of gaseous formaldehyde have been developed. One is a spectroscopic method based on direct fluorescence detection of gaseous formaldehyde following excitation with UV light. This method has been developed to the prototype stage by modifications of a commercial fluorescence SO2 detector to convert it to formaldehyde detection. The prototype spectroscopic formaldehyde monitor exhibits a detection limit of <30 ppbv, with a time response of about one minute. The second method is based on derivatization of formaldehyde in aqueous solution to form a fluorescent product. The detection of fluorescent product was made more sensitive by using intense 254 nm light from a mercury lamp for excitation, thereby allowing use of a simple and efficient glass coil scrubber for collection of gaseous formaldehyde. The wet chemical formaldehyde monitor incorportating these improvements exhibits a detection limit for gaseous formaldehyde of 0.2 ppbv and for aqueous formaldehyde of 0.2 micromolar with time response of about one minute, following a lag time of 2 minutes. Both instruments were tested in the laboratory with gaseous formaldehyde standards, and the aqueous scrubbing/analysis method was field tested by continuous operation over a 10-day period in which outdoor and indoor air were sampled for alternate half-hour periods. A comparison of real-time (aqueous scrubbing/analysis) and integrated measurements, using dinitrophenylhydrazine (DNPH) impingers, showed close agreement between the real-time and DNPH data, even at concentrations as low as 1 ppbv.

"EPA/600/3-90/088." "November 1990." Microfiche.