Auxiliary Boiler

Dear gentlemen,
Can any one answer/explain the following

What is the interpretation of “hot standby” for auxiliary boiler?
Are there any restrictions for purging of the aux boiler prior to start-up (firing)?
Hot Standby can be anything you imagine it would be ..

The chemical plant I worked at had hot standby as they were exporting steam to a third party which was the justification. It was retained in a hot state by steam from the operational boiler.

Periodically it was fired to ensure correct burner operation, which in this case was an oil burner system. No purging was therefore required.