If you use any wood or gas appliances indoors, you must ensure that your cabin is properly ventilated. Air vents and trickle vents must be unblocked and kept clear of snow.
Burning gas or wood consumes oxygen. This is why good ventilation is essential when you use gas or wood-burning appliances indoors. An insufficient airflow could result in carbon monoxide poisoning.
Many chimneys now have a special fresh air intake. These chimneys have two passages, one to take exhaust gases out, and the other to bring fresh combustion air in. Fresh air can also be fed directly into a fireplace via a separate duct.
Before lighting the fire or turning on the gas, you must ensure that the air vents and trickle vents are not blocked, and will allow fresh air in. In winter, snow may be blocking the air flow, and you will have to remove it with a shovel. Also check that the flue is not completely covered by snow.
If there's a lot of snow, you should think about how you would escape if your cabin were to catch fire. As well as the main escape route, it's a good idea to clear snow away from alternate routes, in case you need to use these to get out.