A nonconforming use as defined in § 139-2 may continue to be maintained, provided that each of the other requirements of this article are met.

No nonconforming use shall be extended or altered, except when authorized by the Board of Zoning Appeals.

If the operation of the nonconforming use requires a license, a permit, a certificate or any other municipal approval, said license, permit, certificate or approval shall be obtained by the user and posted in a conspicuous place on the premises and shall be current.

No nonconforming use shall be changed to other than a conforming use for the district in which it is situated. Once a nonconforming use is changed to a conforming use, the right to maintain such nonconforming use shall be lost, and there shall be no right to revert to a nonconforming use.

Wherever a nonconforming use is discontinued for a period of at least one year, such use shall be deemed abandoned and shall not be reestablished, and any use of the premises thereafter shall meet the requirements of this chapter as to the zone in which such property is located.

A nonconforming use shall be maintained in such condition as will not constitute a danger to the safety, health or general welfare of the public.

If a nonconforming use is damaged, destroyed or demolished to an extent greater than 50% of the fair market value of the improvements as they existed immediately before the damage, destruction or demolition, same shall be razed by the owner, and the right to conduct any nonconforming use thereon shall terminate as of the time of the damage, destruction or demolition.