Quantitative relationship between airborne viable and total particles

The numbers of viable and total particles in a microbiological laboratory and in a class 100,000 clean room were examined for a predictable relationship to aid the monitoring of airborne microbial contamination. Six-stage Andersen samplers were used to enumerate viable particles and a modified Royco particle counter was used to enumerate total particles. Over 99% of the total particles present in both areas were less than 1 micron in size; however, only 1 in 10,000 of the particles this size were viable. At the other end of the particle size scale, it was found that less than 0.1% of the total particles were greater than 5.4 micron in size, but only 4.5% of these particles were viable. Viable particles make up only a very small portion of the total particles making any correlation undetectable. An analysis of the combined data from both areas using only total and viable particles over 5.4 micron showed a positive correlation. An analysis of the data from each area individually showed no correlation. Estimation of viable particulates from enumeration of total particulates in the large particle ranges may be possible only in areas where a high degree of environmental control is exercised.