Microbial Assessment of a Single Fumigation by Formaldehyde of a Multi-Level Animal Facility

Abstract

A six level laboratory animal facility with basement and a plant room on the roof had been vacated for a period of 18 months for complete refurbishment. With the installation of new doors, floors, furniture, and air conditioning systems, the building had been open to ingress by wild birds, rodents and insect pests. Before reoccupation it had to be rendered as microbiologically clean as possible. Immunologically suppressed animals and medium term research projects might be compromised if unappreciated levels of potentially pathogenic organisms were to remain within the fabric of the building. It was decided to fumigate with formaldehyde, to sterilise all surfaces as well as sub-surface structures, ducts and conduits. After careful consideration it was decided to carry this out as a single operation. Wind tunnel tests on a model indicated that effluent air, discharged in a high velocity jet from roof level, did not return to street level, even under a variety of wind conditions. Calculations showed there would be an immediate and considerable dilution factor on the discharged air so that it would be possible to generate sufficient vapour to sterilise the 54 main areas involved and to remove the vapours without risk to staff, operatives, passers-by, or the general environment.