All factory built gas appliances must be installed in accordance with the approved manufacturer's installation instructions. That is the only place you will find reliable information. It should be available on the internet.

If this is a fireplace do not install it in a bedroom or bathroom even if it is legal to do so which in many states it is not.

Sometimes even if you can do something, you shouldn't.

I would never do a ventless gas fireplace.

I would be irresponsible if I did not comment. A PhD toxicologist I know (WHO consultant) as a result of family members having carbon monoxide poisoning in my previous home, told me "There is no such thing as a safe, ventless fireplace." I built 5 years ago and used a vented gas fireplace and did extensive reading on all types before I made my decision. And I am still very careful and have multiple CO detectors. Ventless FP's are legal in my state but eventually will be illegal everywhere. 2-3 hours of reading on the subject and you will know also! Google, "Are ventless gas fireplaces safe" and don't read anything by their manufacturers. Good luck!

Ventless fireplaces are not allowed in bedrooms and bathrooms in Massachusetts. Until recently, they could not be sold in the state. There are powerful lobbies trying to get these killers approved in every state.

The one that is being asked about is electric, and with reviews as noted above by SpringtimeBuilders - very little heat, glass defect with no customer service...

https://www.amazon.com/Regal-Flame-Lexington-Fireplace-Fireplaces/dp/B01MSBZI00

"Specifications
Smokeless Ventless Wall Mounted Recessed
Built In Electric Fireplace Insert with Heater, Touch Pad with 3
settings of high, low, and no heat (only

Wall mounting hardware included; Remote
included to control the flame and heat (batteries not included).

Includes a powerful fan-forced heater. This
recessed electric fireplace heater requires no ethanol, gas, chimney,
mantel, stove or gel cans.

Timer offers automatic shut off of 30
minutes to 7.5 hours. This indoor built in electric fireplace insert is
completely vent free and perfect for any

Overall Dimensions: 36W x 5.5D x 21.4H
Inches - Flame View Dimensions: 30.9W x 12H Inches - Firebox Dimensions:
32.5W x 20.17H x 5.5D Inches."

If it is electric, then it is really an electric heater and the only thing that would matter is if you like the look when it is on and what the installation instructions are to install it the way you want it. Should be online info.