What is an example of a compressed gas frequently found on construction sites?

Propane is indeed a commonly used compressed gas on construction sites, primarily because it serves as a fuel source for heating and powering various types of equipment. It is utilized in portable heaters and as a fuel for certain types of machinery. Propane's properties make it suitable for outdoor use, where it can be stored in portable tanks and is readily available.

In the context of construction, the other gases listed, such as helium and chlorine, have specific applications but are not frequently encountered as part of the standard operations or common practices on construction sites. Carbon dioxide is sometimes used for specific applications like extinguishing fires, but it is not as prevalent as propane in daily construction activities. Thus, propane stands out as the primary example of a compressed gas you would typically find on construction sites.