When piping is fabricated, it forms a heavy oxide layer during hot working. This layer is known as mill scale and must be removed from critical systems before putting them in to service. Over the course of time, enhancements have been made to the techniques in the detailed engineering analysis used by plant start-up to perform steam blows. During any plant start up, there is the possibility that particles left in the pipe from the construction phase could break loose and travel downstream. These particles could subsequently damage instrumentation and impede other plant operations. The theory behind steam blowing is to ensure that during the steam blow, the piping experiences a dynamic pressure at least 20% greater than it would during normal operation (CFR > 1.2). This ensures that anything left behind after the steam blow will not come loose during normal operation.

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The time taken for an object to travel throughout the system and be ejected cannot be calculated. Instead, a technique of detecting particles in the emerging steam blow is used. This technique checks the emerging steam for particles impacting on a polished metal plate (commonly known as a target).

The steam blow method is similar to the exhaustive air blow technique, except the boiler is fired to generate the pressurised steam used to clean the steam path. Specialised quick opening valves and a detailed procedure along with the design of temporary spools, steam quenching devices, silencers, and debris containing equipment are required to perform this service.

For pre-commissioning, a continuous low-pressure steam blow technique has become standard practice for the cleaning of most steam system circuits. This method requires the steam generators to be continuously fired to generate steam velocities that are 5 to 7 times greater than the velocities generated during normal plant operations.