***** "ClO2 at 10 μg ml−1 effectively reduced conidial germination of all decay fungi tested after treatment for 0·5 min. Chlorine dioxide only kills by contact, not systemically, and is effective only on exposed fungal propagules, such as those suspended in water or on the surface of fruit. It does not kill pathogens under the fruit skin or active infections. Chlorine dioxide can be difficult to use indoors because when a treated water stream is agitated or aerated, some of the ClO2 comes out of solution and enters the atmosphere. There is a permissible exposure level of 0·1 μg ml−1 in the air, but workers will respond to the odour before that level is reached. In USA, for this reason the recommended rate for indoor applications is μg ml−1 or less"