Silent breaching is essentially what it is named, a way of breaching silently so that occupants inside a building are not aware of the officers breaching. 

Essentially all officers get lined up in the correct breaching orders, seen here SCO Breaching structure, but instead of the normal way of saying your set (saying T1 set, T2 set etc out loud) you would say it in radios.

Additionally you would not give any warnings, in order to have an additional element of surprise, so it requires all round teamwork and you must utilize communications in radios. 

Silent breaching can ONLY be used when it is deemed necessary by other SCO-19 and CTSFO Command.  

A good example of Silent Breaching: 

You have received information that two gangs are doing a drug deal in a building, and the officers breaching the building need an element of surprise so they set up for a silent breach. 

A bad example of Silent Breaching: 

You arrive at a store robbery alone and decide to silently breach in order to surprise the person inside. 

Basically, always follow a SCO-19 or CTSFO Command lead whether you should or should not silently breach, never silently breach alone and never silently breach on store robberies. 

PLEASE NOTE THAT THIS IS ONLY ABLE TO BE DONE IF AUTHED BY SCO-19 OR CTSFO COMMAND.