A firelacer can use their abilities any time they can breathe and have access to air. A firelacer cannot initiate any firelacing effects while underwater, or anywhere else where their body is completely covered.
The most important distinction for lacers is that a lacer must be close to a substance they can lase in order to perform any of their abilities. These restrictions are outlined below, but are left to the DM's discretion as to what exactly is possible based on the situation and environment.