Which type of private fire department primarily operates on a subscription basis?

The type of private fire department that primarily operates on a subscription basis is the one that is nonprofit. Nonprofit fire departments often rely on subscriptions from local residents or businesses to fund their operations. In a subscription model, individuals or businesses pay a fee to receive fire protection services. This model allows the department to operate without relying solely on government funding or taxation, making it a viable option for those in areas where municipal fire services may not be available.

In contrast, private fire departments serving small airports, operating under government contracts, or those that serve private businesses typically do not rely on subscription fees in the same way. They often receive funding through contracts, grants, or other commercial means rather than from individual subscriptions, which is what distinguishes the nonprofit fire departments.