Zone 2 As a place in which an explosive atmosphere consisting of a mixture with air or flammable substances in the form of gas, vapors and mists is not likely to occur in normal operation but if it does occur, it will be present for a short period of time only.
Zone 22 as a place in which an explosive atmosphere, in the form of a cloud of combustible dust in air, is not likely to occur in normal operation but, if it does occur, will persist for a short period only. For example, leaks from incorrectly fitted lids or spillages.