No gathering or entertainment shall be held or presented in any premises other than a building as described in the preceding section, unless the premises have been examined by the Village Police Chief or Building Inspector not more than 3 days before the date of the gathering and found to be free of any fire hazard and found to be suitable for the purpose. No structure enclosed by a roof shall be used for that purpose unless the same is constructed of non-flammable materials; provided that tents or structures covered by canvas or similar material may be so used if the canvas or other material has been properly treated so as to be rendered fire resistive. ('68 Code, § 75.02)