Can you use a heat mat with reptile carpet?

There's a clue in the name — a heat mat heats objects up. In fact, it's not really recommended to even have much substrate over a heat mat, let alone a tank carpet. Not only is it a fire risk, but, by putting down what effectively becomes a heat barrier, you risk the vivarium not actually getting up to temperature.

Read in-depth answer here. In respect to this, where should a reptile heat mat be placed?

The heat mat should be placed in the hot zone of the vivarium. It should cover approximately 1/3 of the floor space and definitely no more than 1/2, as you must allow your pet to move to a cooler area if it is getting over heated. The heat mat is either mounted on the side of the tank, or on the bottom.

Also Know, can I put a heat mat under substrate? It is not advised to put a heat mat under substrate in a vivarium as it stops airflow across the heat mat which can lead to a thermal build up. Ideally is should be under the viv with the viv raised up 5mm above it or on the back wall of the vivarium.

Furthermore, can you put a heat mat inside a vivarium?

Heat mats and strips can be used on the bottom, side or top of a vivarium or terrarium. If used with a wooden vivarium then they must only be used inside the vivarium. If they were placed on the outside then the wood insulates the mat and slows the heat getting into the vivarium where it is needed.

Are reptile heat mats a fire hazard?

Properly designed and manufactured heat mats should NEVER pose any risk of fire.