Twice in two days we have had postings about vermin intrusion into the ZC cabinet via the intake port and outside air intake vent. Even if you have no issues, go out and check the outdoor intake and make sure it is securely screened, preferably with a stainless steel mesh. If there is no screening, get it done. The risk is losing the ZC fireplace due to unremovable debris, nuts or bodies trapped inside the metal cabinetry. Failure to do this can be very expensive!