Section R. 400.4520 - Interior finishRule 520.
(1) The following alphabetical classification of finished materials for flame spread and smoke development, as determined by the tunnel test in accordance with the national fire protection association, standard No. 255, 2006; American society of testing materials E-84-07, 2014, or underwriters laboratories standard No. 723, 2008, shall be used to determine interior finishes: | Class | Flame Spread | Smoke Developed |
| A | 0 - 25 | 0 - 450 |
| B | 26 - 75 | 51 - 450 |
| C | 76 - 200 | 126 - 450 |
The same alphabetical classification is also used for combustibility of prefabricated acoustical tile units, only under federal test number SS-5-118a.
(2) Interior finish includes the plaster, wood, or other interior finish materials of walls; partition s , fixed or movable; ceiling; and other exposed interior surfaces of the facility, other than nominal wood trim.(3) The classification of interior finish materials as to their flame spread and smoke development shall be that of the basic material used, without regard to subsequently applied paint or other coverings, except where such paint or other covering is of such a character or thickness where applied so as to affect the material classification. Finishes such as lacquer, polyurethane-based materials, or unapproved wall coverings shall not be used.(4) In a new constructed, remodeled, or converted facility, an interior finish classification shall be that of the basic material used, without regard to subsequently applied paint or other covering in an attempt to meet the classification.(5) Interior finish materials in facilities shall be as follows:(a) In small and large open facilities without a sprinkler system, class A or B in exit ways and class A in seclusion rooms. In all other areas, at least class C.(b) In open facilities with a sprinkler system, at least class C throughout, except in a seclusion room.(c) In secure facilities, class A throughout regardless of automatic sprinkler protection.Mich. Admin. Code R. 400.4520
1983 AACS; 2015 MR 9, Eff. June 8, 2015