Uses designated in this title as conditional uses shall be permitted, enlarged, or altered only upon approval of the planning commission in accordance with the standards and procedures specified in this chapter. Conditional uses are those which may be appropriate, desirable, convenient, or necessary in the district in which they are allowed, or which by reason of their height or bulk or the creation of traffic hazards or parking problems or other adverse conditions may be injurious to the public health, safety, welfare, comfort, and convenience unless appropriate conditions are imposed.