Unused is not the same as unchanged
During years without use, water, animals, corrosion and building work can affect a chimney. The appliance may also have been disconnected, altered or intentionally taken out of service. Do not start with a small test fire to find out whether it works.
Look for records and ask previous occupants what they know, but label uncertain details as unknown. A professional needs to distinguish documented history from recollection.
Identify the intended use
Tell the company whether you want to use the existing fireplace, install a stove or convert to another fuel. These are different projects. An inspection of current condition does not automatically approve a proposed new appliance.
Gather accessible model information and photographs of the room, appliance and exterior from ground level. Do not open sealed passages or dismantle vent components to improve the description.
Request an assessment before cleaning alone
Ask which inspection level fits the unknown history and intended use. The scope should consider the appliance, connected flue, accessible structure, termination and potential obstruction. Cleaning may be required to examine surfaces, but it is not the whole decision.
If damage or inaccessible construction prevents a conclusion, request a written explanation of the uncertainty and next investigation. Be wary of a simple 'ready to burn' statement that does not identify the system or limitations.
Resolve findings and learn the appliance
Complete necessary work and retain the closeout record before use. Obtain the correct appliance instructions rather than relying on advice for a different fuel or model. Ask the professional to explain maintenance tasks, service intervals and any operating restriction.
Maintain alarms and household escape planning separately from the chimney appointment. If smoke enters the room or a CO concern develops, stop use and follow emergency guidance rather than continuing because a service was recently completed.