The state fire marshal shall have the power to grant exemptions from the application of specific requirements of regulations promulgated pursuant to this act. Any such exemption shall be granted only upon written request which clearly demonstrates that the enforcement of a specific requirement of a rule or regulation will cause unnecessary hardship to the petitioner, or that such exemption is necessary for the petitioner to take advantage of new methods or equipment of recognized adequacy which conforms to fundamental safety standards. The particulars of any exemption so granted shall be set forth in writing, and a copy thereof shall be retained in the office of the state fire marshal.