A nonconforming use is hereby required to be maintained in such condition as will not constitute a danger to the safety, health or general welfare of the public. Alterations and extensions of the nonconforming use in order to comply with the provisions of this section are permitted, provided that such alteration or extension shall not tend to increase the inherent nuisance, nor shall such alteration or extension violate any provisions of this chapter regarding yards, lot area or lot coverage for the district in which it is situated or increase any existing violation of such provision.