HFCs were developed as substitutes for ozone-depleting substances (like CFCs and HCFCs) in various applications. 1. Aerosols HFCs are used as propellants in various aerosol products. 2. Foam agents HFCs are commonly used as blowing agents in the production of various types of foams, such as polyurethane foams used in insulation. 3. Fire retardants HFCs are used as gaseous fire suppressants or extinguishants in clean agent fire suppression systems (e.g., HFC-227ea, HFC-125). While the term 'fire retardant' can sometimes refer specifically to additives in materials, in a broader sense related to fire safety, HFCs function to suppress fire. 4. Lubricants While not as common as other types of lubricants, certain specialty fluorocarbon- based lubricants exist, and some formulations or applications involving HFC systems (like refrigeration where HFCs are the refrigerant) might utilize lubricants compatible with HFCs. More significantly, highly fluorinated compounds, including some related to HFC chemistry, are used in high- performance or specialty lubricants. Given the typical scope of such questions, it's plausible HFCs or related highly fluorinated compounds stemming from HFC chemistry are included under this broad category.