All electronic equipment to be used in these locations must be tested by an independent lab and certified to be safe for use. They generally look at the schematics of the equipment to verify that even in a failure condition the equipment will not create a spark that could ignite the hazardous atmosphere.
Digi radio modems have been integrated into many products that are used in hazardous environments. For electronic equipment to be used in environments with combustible gasses present, it is often necessary for the final product to receive a UL or CSA certification for hazardous locations. These locations are rated by how hazardous they are. Class I, Division 1A (C1D1A) is the most dangerous location. An example of a C1D1A location would be a location in direct contact with acetylene gas. The area close to an unleaded gasoline pump is usually considered a C1D2 location.