There are numerous ways to measure microbial contamination of water, and USP recommends specific ways of doing so for pharmaceutical waters. Traditionally plate count methods are widely used for releasing water; however, they are prone to error and can take 5-7 days for results. Plate counting also requires the formation of a colony of bacteria on a plate and hence the measurement unit is called 'colony forming unit" or CFU, which is an estimation of the total number of bacteria present in the sample plate. Another way of measuring microbial contamination in water is through laser-induced fluorescence, with a microbial detection analyzer. These analyzers uses laser induced florescent technoly to measure the total number of cells that are present in the sample volume of water. Systems that uses this type of technology allow for at-line, real-time monitoring of microbial contamination in pharmaceutical waters by identifying cells present in the sample water immeditely and is reported as auto fluorescent units (AFUs).