Controlled formaldehyde fumigation system.

A comparative study of formaldehyde (HCHO) fumigation was carried out by controlled vaporization, using an electric vapor generator, and by the Formalin-permanganate method. Determination of vapor levels as well as bactericidal action showed the generator to be more effective. Maximum achievable fumigant levels were temperature dependent and related to the equilibrium vapor concentration of HCHO. At a room temperature of 21 degrees C, vaporization of more than 2,000 micrograms of HCHO per liter resulted in conversion of HCHO to paraformaldehyde, which condensed on surfaces and contributed to prolonged residual vapor levels. An electronic monitor is described which is capable of detecting HCHO levels as low as 10 microgram/liter and can be used to monitor the complete fumigation process.