The currently recommended methods for the formaldehyde fumigation of rooms have been studied with the aid of an instrument designed to monitor the temperature, humidity and formaldehyde concentration. The results show that although the procedures are generally effective as measured by microbiological methods the conditions within the areas treated are not those expected from calculations based on the room volume and the amount of formaldehyde used. The measured formaldehyde levels in particular are much lower than predicted and indicate that formaldehyde vapour may be effective at lower concentrations than previously supposed.

A statistically based comparison of five methods of enumerating bacteria in foods has been undertaken to assess the potential application of the Spiral Plate Maker (Gilchrist et al. 1973) which is claimed to reduce very significantly the costs involved in the quantitative estimation of viable micro-organisms in foods. The performance of the Spiral Plate Maker was compared with that of three conventional methods (pour plate, surface spread plate and drop count) for the examination of four types of food by four different operators. Analysis of variance showed that there were no differences between the methods at the 5% level although some isolated interactions occurred. Regression and correlation coefficients between the various methods were all highly significant and the results obtained by the spiral plate method were within the limits of error for traditional quantitative methods. The spiral plate method, in many cases, can replace advantageously any of the other methods for the quantitative estimation of viable microorganisms in foods. Labour requirements for the enumeration of micro-organisms by the spiral plate method were only 31% of that required for one conventional method. In addition considerable savings in materials were achieved.(1491

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The effects of exposure of spores of Bacillus globigii NCTC 10073 to controlled levels of formaldehyde vapour under varying environmental conditions are reported. The death rate of the micro-organism varies with the humidity and formaldehyde concentration and can be predicted for conditions within the limits of the information available. A mathematical model for the effects of formaldehyde is proposed which can be used to calculate the effects of known conditions and as the basis of a controlled formaldehyde fumigation process. Results of practical tests of such a process are described.

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