Smoke Detection, Penetration, and Evacuation Tests and Related Flight Manual Emergency Procedures

1/6/94 AC 25-S-A Appendix 1 APPENDIX I This appendix addresses those rules that may be complied with by the use of smoke detection tests, smoke penetration tests and smoke evacuation tests.

This appendix discusses the rules as they relate to the specific test.

Certain rules that are complied with by measuring gas concentrations are discussed in a cursory manner, as well, to show that these rules are not to be confused with rules requiring compliance by smoke detection, smoke penetration and smoke evacuation tests.

Section 25.831 has been applied, in the general sense, in consideration of normal operating conditions and failures that could expose the passengers to harmful or hazardous concentrations of gases or vapors. Fuel fumes are to be included in the evaluation [ref. 4b.371]. Smoke, caused by failure, is part of this consideration. Hazardous concentrations of mixed gases and vapors from combustion (smoke) have not been defined. See the discussion under compliance with§ 25.857(b).

Section 25.83l(b)(l), originally in§ 4b.371, addresses exposure to carbon monoxide. Section 4b.371 also addressed fuel fumes and made reference to § 4b.467 [Exhaust system and installation components]. Section 25.83l(b)(I) was written to cover carbon monoxide exposure from fuel systems, powerplants and combustion heaters during normal operation and failure conditions.

Currently, this rule also applies to ventilation air from turbojet or APU bleed air systems. Methods of compliance with§ 25.83l(b}(l) are not the subject of this AC.

Section 25.83l(b)(2), originally in§ 4b.371, addresses exposure to carbon dioxide. The original intent was to address temporary exposure to carbon dioxide extinguishing agent and to define an exposure level when protective breathing equipment should be used. Currently, this specific portion of the rule is under review. Methods of compliance with§ 25.83l(b)(2} are not the subject of this AC.

Section 25.83l(d) addressed the accumulation of hazardous quantities of smoke in the cockpit area. Hazardous quantities of smoke have not been defined.

Common certification practice has been to assume that limited electrical fires [possibly other fire sources] within the cockpit or connecting electronic bays may generate enough smoke to be considered hazardous. The cockpit smoke evacuation procedures, addressed in this AC, have been devised as a method to comply with§ 25.83l(d).

Section 25.851 addresses exposure to extinguishing agents from both portable and built-in extinguishers. This rule can be applied generally where coverage is not provided in other specific rules, for example,§ 25.1197, under "Power Plant Fire Protectiontt and§ 25.857, "Cargo Compartment Classification."

Verifying exposure concentrations of extinguishing agent applied within an occupied compartment is not the subject of this AC.

Section 25.855(h) establishes the use of flight test when showing compliance with§ 25.857 (cargo compartment accessibility, penetration of hazardous I

AC 25-9A 1/6/94 Appendix 1 quantities of smoke into occupied areas, and dissipation of extinguishing agent in Class C compartments).

Compliance with§ 25.857(b)(2), {c)(3), (d)(2) and (e)(4) is one subject of this AC, i.e., showing there are means of excluding hazardous quantities of smoke, flames, or extinguishing agent, from any compartment occupied by the crew or passengers.

One method of showing there are means of excluding hazardous quantities of smoke and extinguishing agent would be to define all the probable combustion sources within the cargo compartment and combinations of combustion byproducts combined with and without the extinguishing agent, and show that the possible exposure concentrations of these byproducts and extinguishing agents will not exceed human tolerances. In addition to the complication of trying to define the concentrations of all the probable combinations of combustion byproducts and extinguishing agent, the complication exists that the acceptable human tolerance to various combinations of combustion byproducts and extinguishing agent have not been defined. For these reasons, this approach to compliance with§ 25.857(b)(2), (c)(3), {d)(2) and {e)(4) has not been attempted.

As a practical method of showing .there are means of excluding hazardous quantities of smoke, flame or extinguishing agent, from any compartment occupied by the crew or passengers, the FAA has accepted the use of flame barriers and demonstrations showing the prevention of smoke penetration into occupied areas, i.e., smoke penetration tests.

A small amount of smoke is allowed into the passenger compartment, if a crewmember has to enter into the Class B cargo compartment from the passenger compartment. See the discussion in the Cargo Compartment smoke penetration tests, see lle.(4).

Section 25.1301 requires that installed equipment function properly when installed. Smoke detection tests and smoke evacuation tests have been used to show that the detection and ventilation systems of galleys, lavatories, and crew rest areas function properly.

Section 25.1309 requires consideration of failures and the effects on occupants. See AC 25.1309-lA. Section 25.1309 is a rule of general applicability which may be applied where specific rules do not apply.

1/6/94 AC 25.9A Appendix 2 APPENDIX II PAPER TOWEL BURN BOX SMOKE GENERATOR The smoke detection testing conducted for crew rest and lavatory areas employing ionization type detection systems uses a smoke generator named the "Burn Box" which is described in the attached figures I through 4. The Burn Box consists of an aluminum outer containment box, approximately 9.5" square (figure 1), surrounded/supporting an aluminum inner burn chamber 6.5" X 5.6 X 8.0" (figures 2 and 3). The top (hinged) surface of the inner chamber is a fine mesh steel in order to help contain the ashes of the burning fuel.

Quarter sheets of standard 10" X 13.5" lavatory paper towel are folded accordion style (figure 4) and alternately stacked into the inner burn chamber. A match hole is provided on the side of the inner box, with access to this hole by way of a hinged side of the outer containment box. Once the fuel charge is ignited, the hinged side of the containment is closed and the hinged top lid of the outer containment box is opened to allow the smoke to begin escaping from the generator. The time to detection begins at this point.

DESCRIPTION OF OPERATIONS CAUTION: Provide temporary fire resistant protective coverings for any decorative surfaces or flammable materials which could be affected by heat or smoke from these tests.

(1) Place Burn Box generator(s) at the critical location within the compartment to be tested.

(2) Open top door of the box.

(3) Open top door/screen of the inner box.

(4) Place desired number of folded 1/4 sheets of paper towels (CROWN C-FOLD 241 towels folded accordion style) uniformly on the screen inside the inner box.

(5) Close top door/screen of the inner box.

(6) Close top door of the outer box.

(7) Open side door(s} of outer box(es).

(8) Ignite paper towels inside generator by extended lit match through 3/4 inch diameter hole through front side of inner box (accessible through open side door of outer box). After paper towel{s) are lit, close side door.

(9) After all generators are lit, simultaneously open top door(s) of outer box(es) to release smoke.

(10) Begin time to detection when all box(es) are opened fully.

AC 25-9A 1/6/94 Appendix 2 SELECTING NUMBER OF BOXES TO USE (I} Crew rest areas utilizing ambient Ionization-type smoke detection systems: (a) For volumes up to 500 cubic feet use 2 burn boxes with a total of 3 paper towels (see description of operation step 4) 6 quarter sheets folded accordion style in each box. Light ejther simultaneously or sequenced up to 15 seconds apart.

{b) For volumes greater than 500 cubic feet: scale up fuel (paper towels) by adding 1.5 paper towels for each additional 150 cubic feet. Add Burn Boxes as required, to maintain control of the flame exiting the top of the Burn Box during testing.

{c) Crew rest areas enclosed with curtains, using Ionization type detectors.

{i) If designed with one detector in each bunk, use one burn box with one full sheet of paper towel.

(ii) If crew rest is designed to have one detector protect more than one bunk, use method described in {l) (a) or (b) above, depending on the volume enclosed.

(2) Standard Lavatory with ambient Ionization type detectors: One Burn Box with 1 sheet of paper towel as fuel placed near the waste receptacle.

1/6/94

AC 25-9A

Appendix 2

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1/6/94

Appendix 1

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