Review Consideration Standard. In considering all appeals and all proposed variations to this Chapter, the Board shall, before making any finding in a specific case, first determine that the proposed variation will not constitute any change in the Zoning Map, unless herein provided by this Section, and will not impair an adequate supply of light and air to adjacent property; or unreasonably increase the congestion in public streets; or increase the public danger of fire and safety; or diminish or impair established property values within the surrounding area; or in any other respect impair the public health, safety, comfort, morals, and welfare of the City. However, no variance shall be authorized unless the Board of Adjustment determines, after public hearing notice and hearing pursuant to Section 400.660, that the requirements set forth in this Chapter have been satisfied.