It is sometimes possible to run part or all of a consumer's load on straight (undiluted) propane vapor. This normally requires separate distribution piping and modifications to each appliance burner train. Large, centralized loads such as boilers are candidates for this approach.

Propane-air is the more universal approach to standby fuel. By mixing approx. 55% propane and 45% air, a gas is produced that performs well in natural-gas burners without individual adjustment. The mix is injected into the natural-gas system as partial or full replacement.

There are several approaches to mixing propane and air, and many blender (mixer) options can be considered. The mixer type influences selection of other equipment used in the system. Common types of propane-air blenders with related mixed-gas pressure ranges are shown in the diagrams below. Note that systems and controls vary widely, and configurations are not shown in complete detail.