Manuals for operating gas fireplaces are usually available on the websites of fireplace manufacturers, as in the cases of Majestic, Heatilator, Regency and Mendota. These manuals are often in PDF format, and are listed according to fireplace name or number.
Majestic categorizes its gas fireplace manuals under the headings of Gas / Vent Free, Gas / B Vent and Gas / Direct Vent. Under each heading are links to the manuals for each model, such as the Lexington LX36DVP or the Pearl STLDVPSC under the Gas/Direct Vent heading. These manuals contain both instructions and diagrams for fireplace operation and safety.
Heatilator has separate drop-down menus for fireplace installation manuals and fireplace use manuals. Models include AZTEC, 3336 and Birmingham 36-B. Regency has manuals for both gas burners and gas fireplaces, with a select number of manuals available in French. The manual charts show product names, product revisions, manual PDF links, revision codes and the dates that each model went into effect. The website also has a similar chart for discontinued manuals, which may be useful if you have an older model.
Mendota has both English and French manuals. The company also provides installation and operation manuals for its gas fireplace inserts, heat management tools and medallion free-standing gas stoves.