Classified as the official "standard for fire doors and other opening protectives", this safety rating applies to the installation and maintenance of swinging, sliding, rolling and hoistway doors, as well as any fire doors, access doors, chute doors, or fire exit windows that allow people to exit or enter your building. NFPA 80 regulates these openings to make sure your building can prevent or slow down the spread of fire and smoke, at least until occupants have exited safely.
This installation standard applies to smoke door assemblies in particular. Unlike fire doors, smoke doors are primarily built to stop the flow of smoke. The NFPA enforces this code to prevent people from inhaling too much smoke, but doors and other openings that meet this standard will also help protect your property from smoke damage.
You're responsible for making sure your building meets the NFPA's fire and smoke requirements. However, NFPA 252 is up to the manufacturers and laboratories that actually test your doors and determine their ratings. This standard is enforced to make sure door openings can regulate the spread of fire. "Fire" technically includes the flames themselves, the rise of indoor temperatures, and the presence of hot gases.