Fire pits are structures specifically built to contain a fire in an enclosed space. They can be manufactured commercially or built by a homeowner. Government regulations for using a fire pit vary by municipality, so check with local authorities before burning.
There are a variety of types of restrictions on burning. In some locales, homeowners can burn in fire pits without a permit, as long as the pit is located a specific distance from a structure and is within size limits. In other areas---such as the entire state of New Hampshire---homeowners need to purchase a permit to burn in a fire pit. The permit may be good for an entire year, however.
The purpose of burn permits is to notify fire and public safety officers that there will be a fire in the area. This allows officials to be on alert for any problems, and allows them to reassure neighbors or other citizens who may call concerning smoke.
Before burning, check with the local municipality. This may be the county, city or township in which you live. Sometimes the administrative office handles fire permits and the fire department handles the paperwork. It is best to assume some kind of permit is required and call, before burning. Also, calling ahead may allow you to gain insight into other rules, such as not burning garbage or construction debris.