Carbon monoxide is the odorless killer that can result from a malfunctioning fuel-burning appliances, not the LP or NG itself.

First, in my opinion, the cheap off the shelf windows cause more problems from seams or locks malfunctioning right out of the gate.

Assuming you've already made sure there is not a ghost with the munchies, its either a setting that was improperly setup (like a timer accidently programed to turn on at a set time) or something is malfunctioning.

-Property managed and oversaw the repair of malfunctioning HVAC units, refrigerators and garage doors.

Clogged or malfunctioning pressure regulators.You may have a pressure regulator on the main pipe coming into the home.

If the property becomes flooded and it's due to a malfunction in the house,, then until it's corrected the landlord needs to either accommodate the tenant in a hotel until repairs are completed if the property is so bad they can't possibly stay there until the property is restored while being worked on .. but this depends also on what is reasonable time...If the property, is or has, become so terribly flooded and the damage is such the owner has determined it will take extensive and lengthy time to fix, then he can negotiate with tenant to be immediately let out of lease. and refund the rent from day of damage to end of month and fully refund the deposit if the damage was not caused by the tenant.IF THE tenant damaged the property due to neglect , malicious act.

Stuff happens so 2 weeks is long, do something consistent with the amount of inconvenience for the septic if they had little or nothing to do with the malfunction.

Heat tape is just one more thing in the house or malfunction or break.

It hasn't been revealed if there was a CO detector, sometimes people unhook them when they think it is malfunctioning because they don't smell anything.

Then I tell the tenant to let me know if any need batteries or replacements (chirping, malfunction etc, etc).