Appendix 2 – Fire Test Procedures for Toxic Gas Generation
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Statutory Documents - IMO Publications and Documents - International Codes - 2010 FTP Code – International Code for Application of Fire Test Procedures, 20101 – Resolution MSC.307(88) - Annex 1 – Fire Test Procedures - Part 2 – Smoke and Toxicity Test - Appendix 2 – Fire Test Procedures for Toxic Gas Generation

Appendix 2 – Fire Test Procedures for Toxic Gas Generation

Parent topic: Part 2 – Smoke and Toxicity Test

1 Scope

  1.1 This appendix specifies methods of measurement of gases developed in cumulative smoke/fire test, using Fourier transform infrared spectroscopy (FTIR). Particular attention is given to the gas sampling systems and conditions of gas measurement.

  1.2 It should be noted that there are fire effluents other than gases, such as particles, smoke or vapours, which may be toxic and that some gases such as hydrogen halides may be trapped by moisture in sampling lines or by filters designed to remove only smoke particles.

  1.3 Gas measurements by FTIR shall be carried out when the maximum smoke density is obtained. That time is determined by a smoke density measurement tests carried out in accordance with appendix 1.

2 Normative References

 The following normative documents contain provisions which constitute provisions of this appendix:

  • ISO 5659-2, Plastics – Smoke generation – Part 2: Determination of optical density by a single-chamber test.

  • ISO 13943, Fire safety – Vocabulary.

  • ISO 19702, Toxicity testing of fire effluents – Analysis of gases and vapours in fire effluents using FTIR technology.

3 Terms and Definitions

 For the purposes of this document, the terms and definitions given in standards ISO 13943 and ISO 19702 and the following apply.

  3.1 Maximum smoke density sampling time (DmST) is the sampling time, expressed in seconds, used in toxicity tests correspondent to the time to reach the maximum specific optical density as per paragraph 2.4.1 of part 2.

  3.2 Sampling Response Period (SRP) is the minimum time necessary during the sampling period to completely load the FTIR gas cell including the time to transfer the effluents flow from the smoke chamber into the cell.

4 Principles

 Fire effluents are sampled from a cumulative smoke chamber of a smoke test (appendix 1) at a single time point called Dm sampling time (DmST) which is pre-determined by the first smoke density test in appendix 1. This time represents the time where the smoke density reaches the maximum level during the standard 20 min test. Gas sampling shall be such that the sample represents the gas, the fire effluent, in quality and quantity, in the chamber, and that any effect of gas sampling systems (filters, probes, pipes, tubes and pumps) in minimized. It is recommended to minimize the travelling time and distance of fire effluent through the gas sampling system. A filtering system for fire effluent shall be installed within the gas sampling system to prevent smoke particles from entering into the gas analyser. FTIR shall be used to analyse the sampled gases.

5 Gas Sampling System

 Gas sampling system should consist of probe, heated gas sampling line, filter, valves and sampling pump.

6 Gas Analysis Technique

 An FTIR system as described in standard ISO 19702 shall be used.

7 Calibration

 Calibration of the FTIR system shall be carried out for gases to be measured in accordance with standard ISO 19702.

8 Test Procedures

8.1 Operation before each test

  8.1.1 Check the internal walls condition of the test chamber and eventually clean them removing all dirty layers and particles. The same operation shall be done on the surface of the internal probe for FTIR sampling.

  8.1.2 The inlet of the probe shall be cleaned.

  8.1.3 Keep the filter, gas sampling line and valves and gas cell at the temperature of 150°C to 180°C for at least 10 min prior to the test.

  8.1.4 The wavelength resolution of the spectrometer shall be 4 cm-1 or better. Set the Mid-IR whole spectral region for collection between 650 cm-1 to 4,500 cm-1.

  8.1.5 Close the chamber door, and introduce the air in the chamber into the gas cell of FTIR. Wait for 1 min and record the background spectrum.

  8.1.6 Turn the sampling valve to introduce the open air into the gas cell.

  • Note: It is recommended, before the start of any smoke test on that day, to carry out a dummy gas measurement where the ambient air in the smoke chamber is sampled and analysed by the normal test procedure, and to make sure that no gas is detected. It is also recommended that such a dummy gas measurement be carried out whenever a questionable gas measurement result is obtained. It is also recommended that this screening measurement be carried out after the smoke chamber is cleaned by volatile solvent.

8.2 Operation during a test

  8.2.1 During the smoke density test specified in appendix 1, the sampling shall start by turning the sampling valve to introduce gas in the chamber into the sampling line, at DmST – (SRP x 0.5) (s).

  8.2.2 Wait for a minimum period equal to SRP then collect the spectrum, stop the sampling from the chamber and turn the sampling valve to introduce open air side.

  8.2.3 Continue the smoke density test until a 20 min period has elapsed. To verify the end of the test, ensure that the smoke density peak has already occurred.

  8.2.4 At the end of the test, follow the end of the test procedures described in appendix 1.

  8.2.5 If the smoke chamber pressure drops below the permitted minimum as specified in standard ISO 5659-2 by any phenomena of the combustion of the specimen, the gas inlet valve of the chamber will automatically open according to standard ISO 5659-2. If this happens, this shall be reported.

  8.2.6 If the smoke chamber pressure exceeds the permitted maximum as specified in standard ISO 5659-2 by any phenomena of the combustion of the specimen, the gas release valve of the chamber will automatically open according to standard ISO 5659-2. If this happens, this shall be reported.

8.3 Repeat tests

 In case an additional set of three smoke measurement tests are repeated in accordance with appendix 1, paragraph 8.8.2, in any of the test conditions in paragraph 8.8.1 of appendix 1, gas measurements shall be conducted at the second and third test of the second set of the tests in accordance with this appendix and the test results shall be reported in accordance with paragraph 10.

9 Gas Analysis

9.1 FTIR gas analysis

 FTIR gas analysis shall be carried out in accordance with standard ISO 19702.

9.2 Calculation of concentration correction for acid gases

  9.2.1 Analysis of filtering materials used in the gas sampling line shall be carried out, and total acid gases trapped by the filtering materials (Qa (g)) shall be obtainedfootnote.

  9.2.2 The relative concentration shall be calculated based on the total gas volume (Vs (l)) passing through the filter for the gas sampling period:

Vs = Sfl x St

Where:

  • Sfl is the gas sampling flow rate (l/s),

  • St is the gas sampling time (s).

  9.2.3 Relative volume of the gas (Va (l)) shall be calculated by:

Va = (Qa/PMa) x Vm

where:

  • Vm is the molar volume at standard conditions,

  • PMa is the molar mass of the gas.

  9.2.4 The concentration correction (Cca (ppm)) for an acid gas shall be obtained by:

CCa = Va/Vs x 106

10 Test Results

 The following test results shall be included in the test report:

  • .1 for each test:

    • .1 maximum gas concentration C (ppm) measured by FTIR for each gas listed in paragraph 2.4.2 of this part;

    • .2 gas concentration correction (Cca), if applicable;

    • .3 corrected maximum gas concentration (C + Cca), if applicable; and

    • .4 DmST and SRP;

  • .2 for each test condition (see paragraph 8.8.1 of appendix 1), the average value of the maximum value of the gas concentration measured and corrected, if applicable, at each test condition; and

  • .3 data regarding the test apparatus:

    • .1 the inner volume of the gas cell;

    • .2 the inner volume and the length of gas sampling line; and

    • .3 the capacity of the gas sampling pump.

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