Proudly American
Give the room one unambiguous status
Tell occupants which appliance is installed and what fuel its instructions allow. Remove decorative baskets of firewood or starter logs that could suggest a wood fire is permitted. If the equipment cannot be identified, leave the fireplace unused instead of inviting guests to choose the fuel themselves. This applies even when the gas supply is turned off.
Treat a past wood fire as an incident
If someone has already burned solid fuel over a gas assembly, discontinue use and explain exactly what was burned and where. A technician can assess the affected burner, controls and venting system as appropriate. Do not brush the evidence away, turn on the gas or light a demonstration fire to see whether anything was damaged.
Ask separately about a permanent change
Returning to wood use is a project involving the gas system, fireplace construction and chimney suitability. Moving the log set aside does not address the gas supply or the condition of the former wood-burning passage. Have appropriate professionals identify what would need to change and which local requirements apply before promising a wood fire in a guest listing.