For many years it has been possible to measure the airborne particulate cleanliness of a cleanroom environment in real-time using optical particle counters. Conversely the traditional methods used to detect the presence of airborne microorganisms take many days to yield a result, and are based on techniques that were developed over 100 years ago. Recent innovations have delivered Rapid Microbiological Method (RMM) technologies, providing end users with real-time information,  enabling a real-time response to airborne microbiological excursions .  A brief review of traditional and RMM methods will be presented. The presentation will focus on a new family of RMM, real-time airborne viable particle detection based on Laser Induced Fluorescence (LIF).  This will include a brief overview of the sensing technology, critical instrument performance parameters and application based use scenarios.