Do you Open damper when using gas fireplace?

It depends.

Most gas fireplaces are designed to be used with the damper closed. This is because the damper helps to create a draft that draws air in from the outside and helps to keep the fire burning. If the damper is open, too much air will be drawn in and the fire will burn too hot. This can cause damage to the fireplace and can also be dangerous.

However, there are some cases where it is safe to open the damper when using a gas fireplace. For example, if your fireplace is located in a very drafty room, you may need to open the damper slightly in order to keep the fire burning. Additionally, if you are using a gas log set that is designed to be used with the damper open, you will need to follow the manufacturer's instructions for operating the damper.

If you are not sure whether or not it is safe to open the damper when using your gas fireplace, it is always best to err on the side of caution and keep it closed.