HNG DN S DNG THIT B TH KH C-NES 713

IMPORTANT SAFETY NOTEThis test method requires the use of a gas/air mixed burner in a sealed chamber. The burner must not be left on for more than 2 minutes in order to consume the test material. If the flame is left on for a longer period then a potentially hazardous pressure may result in the chamber. The maximum pressure that the FTT NES 713 Chamber can operate under is 50 millibar (mbar). Models from April 2011 onwards are fitted with a pressure gauge.Should this condition occur, immediately push the Vent button on the control unit, turn the burner gases off and turn on the extraction. If the material has not all been consumed, then the test must be repeated with a smaller mass, so that the burner is on for less than 2 minutes.For this reason the equipment must be supervised at all times.

21. Safety Precautions

General

This test method may involve hazardous materials, operations and equipment. Therefore, we specifically exclude any liability whatsoever for claims arising from use or misuse of the equipment. It is the responsibility of whoever uses this equipment to consult and establish appropriate health and safety practices and determine the applicability of regulatory limitations prior to use.

1. All service inputs must be made secure.

2. The burner gases (methane and air) must be supplied, via approved regulators, with the connections supplied and secured by approved gas hose clips.

3. The mains power must be connected using the cable supplied by Fire Testing Technology. Fuses must conform to Fire Testing Technology specifications.

4. After each run it is recommended that the methane gas is turned off at the source.

5. The equipment must be supervised at all times when in use.

6. Adequate means for extinguishing a fully developed fire should be available.

7. Before opening the chamber door, ensure that the excess pressure inside the chamber is at 0 mbar. For NES 713 chambers without a pressure gauge, the pressure needs to be equalised with the ambient. Relieve the pressure by opening the exhaust vent by pressing the Vent button and starting the extraction fan. After 30 seconds or when the pressure is below 5 mbar, remove the inlet vent plug. Ensure that the exhaust vent has opened by observing the position of the shaft. Note that even a small excess pressure inside the chamber can result in considerable force on the door, which may endanger any person within the radius of swing of a released door.

8. Do not lean on an open chamber door. This is because, when open, the door shifts the centre of gravity and there may be a risk of toppling the chamber.

9. Avoid putting fingers under the exhaust vent when open, or in the mixing fan.

10. When not in use, ensure that the door is secured ajar and that all the on/off ball valves (Gas and Air) are closed.

27Personal Safety Requirements

This equipment must only be operated by authorised personnel who are fully conversant with the safety requirements. The operator must have a thorough knowledge of the chemical properties of the materials under test and what combustion products can be expected from them.

Care should be taken to avoid contact with hot surfaces produced from the burning of the material and the burner. It is recommended that heat-protective gloves (not household rubber) are worn when working in the burner area and when removing a specimen holder from the chamber.

The products of pyrolysis and burning of the materials under test may be carcinogenic, toxic, corrosive, flammable or otherwise hazardous. Residues remaining in the apparatus after the test may also be hazardous (e.g. respiratory, skin, eye). An auxiliary breathing device and protective glasses may have to be worn before opening the chamber door. It may be noted that highly corrosive residues may permeate and degrade heat-protective gloves. Butyl gloves must be worn underneath the heat-protective gloves for complete protection in such cases.

The installation, siting and provision of services to the equipment must have the approval of the Safety Officer.

Gas Safety Information

For additional information please refer to the gas supplier's safety data.

Methane

InhalationPROMPT MEDICAL ATTENTION IS MANDATORY IN ALL CASES OF OVEREXPOSURE TO THIS PRODUCT. RESCUE PERSONNEL SHOULD BE EQUIPPED WITH SELF-CONTAINED BREATHING APPARATUS. Victims should beassisted to an uncontaminated area and inhale fresh air. Quick removal from the contaminated area is most important. If breathing has stopped administer artificial resuscitation and supplemental oxygen. Further treatment should be symptomatic and supportive. Keep victim warm and quiet.

Fire Fighting Measures

FIRE AND EXPLOSION HAZARDS: Flammable gas. Rapid flame propagation and flashback possible. Cylinder may vent rapidly or rupture violently from pressure when involved in a fire situation.

EXTINGUISHING MEDIA: Carbon dioxide, dry chemical or water spray.

FIRE FIGHTING INSTRUCTIONS: If possible, stop the flow of gas. Inerting the atmosphere to reduce oxygen levels may extinguish flame, allowing capping of leaking container. Do not attempt this unless specifically trained. Reduce the rate of flow and inject an inert gas, if possible, before completely stopping the flow to prevent flashback. Do not extinguish the fire until the supply is shut off as otherwise an explosive reignition may occur. If the fire is extinguished and the flow of gas continues, use increased ventilation to prevent build-up of explosive atmosphere. Use non-sparking tools to close container valves.

Use water spray to cool surrounding containers. Be cautious of a Boiling Liquid Evaporating Vapour Explosion, BLEVE, if flame is impinging on surrounding containers. Direct 500 GPM water stream onto containers above liquid level with remote monitors. Limit the number of personnel in proximity of fire and evacuate surrounding areas in all directions.

Firefighters should wear respiratory protection (SCBA) and full turnout or Bunker gear. Continue to cool fire-exposed cylinders until well after flames are extinguished.

Handling and StorageEarth ground and bond all lines and equipment associated with the system. All equipment should be non-sparking or explosion-proof. Methane is non-corrosive and may be used with any common structural material.

Use only in well-ventilated areas. Valve protection caps must remain in place unless container is secured with valve outlet piped to use point. Do not drag, slide or roll cylinders. Use a suitable hand truck for cylinder movement. Use a pressure regulator when connecting cylinder to lower pressure piping or systems.

Do not heat cylinder by any means to increase the discharge rate of product from the cylinder. Use a check valve or trap in the discharge line to prevent hazardous back flow into the cylinder. Do not insert any object (i.e.: screwdriver) into valve cap openings as this can damage the valve causing leakage.

Protect cylinders from physical damage. Store in cool, dry, well-ventilated area of non- combustible construction away from heavily trafficked areas and emergency exits. Do not allow the temperature where cylinders are stored to exceed 125F (52C). Cylinders should be stored upright and firmly secured to prevent falling or being knocked over. Full and empty cylinders should be segregated. Use a "first in-first out" inventory system to prevent full cylinders from being stored for excessive periods of time. Post "NO SMOKING signs in use or storage areas. There should be no source for accidental ignition in areas where this product is being used or stored. Outside or detached storage is preferred.

Do not smoke when handling methane gas.

DisposalWaste gas should be flared through a suitable burner with a flash back arrestor. Empty cylinders still contain flammable vapour and must be returned to the supplier.

2. The FTT NES 713 Apparatus

General

The FTT NES 713 is a closed chamber of fixed volume (728 mm 982 mm 982 mm = 0.702 m3) in which specimens can be subjected to a premixed burner

Provision is made for gaseous/volatile test products to be drawn from the chamber for analysis through ports on the side of the chamber.

The system comprises of the Combustion Chamber, Combustion Control Unit and a Gas Analysis System with colometric tubes.

The client will be required to provide methane and compressed air supplies to the burner and means of ventilating the chamber into existing extraction systems.

Electrical Connection

Electrical connections between the chamber and control unit are made via a multi-core non-reversible cable with a keyed plug and socket at each end. The mains voltage is fed into the unit via a 3 pin socket at the rear of the Control Unit. The socket is fused into a 5 amp fuse. The mains supply must be an earthed 110/230V A.C. (50 or 60 Hz) only, capable of delivering at least 2 amps.

Gas Connection

Gas connections between the chamber and control unit are made via the hoses supplied, the larger bore for the methane and the smaller bore for the air. The air and methane gas is fed into the unit via standard gas connectors at the rear of the unit. The pressure of gas and air going into the unit should be less than 2 bar.

It is recommended that a flame arrester is fitted externally on the combustion chamber, at the coupling between the flexible hose and the cabinet.

The Combustion Chamber

The chamber is made from polypropylene with hinged door and an observation window made from polycarbonate. The nominal volume of the chamber is 0.7 m3.

Figure 2.1: Combustion Chamber

The chamber includes:

Extraction

This consists of an extraction motor mounted on top of the Combustion Chamber and an exhaust vent mounted in the roof of the Combustion Chamber. Both are activated from the Control Unit.

Figure 2.2: Smoke Extraction Unit and Exhaust Vent Solenoid

Sampling Ports

12 or 15 sampling ports are provided (depending on the model) to allow for gas analysis. The ports can be sealed by either linking adjacent ports with a loop of silicone tubing, or by tying off a length of tubing (see Figure 2.3)

Figure 2.3: Sampling Ports

Mixing Fan

A mixing fan is mounted horizontally and centrally inside the chamber at roof level and is switched on and off externally from the Control Unit.

Figure 2.4: Mixing Fan and Vent Solenoid (Open)

Burner

A Bunsen burner with a spark ignter. The burner is supplied with a mixture of methane and air from the Control Unit. The spark igniter is turned on when the gas is flowing and is designed to stop sparking when a flame in detected.

Figure 2.5: Gas Burner and Specimen Support

Specimen Support

A clamp stand holds the specimen support in place over the flame. The support is a metal ring with temperature resistant wires (Nickel-chromium alloy wire 0.5 mm diameter) approximately 10 mm apart to form a lattice.

Figure 2.6: Gas Burner and Specimen Support

Pressure Gauge (Models after April 2011 only)

A 0-100 mbar pressure gauge is fitted to the chamber to show the pressure inside the chamber. The maximum pressure that the chamber can be subjected to is 50mbar.

Figure 2.7: Pressure Gauge

The Combustion Control Unit

The control unit comprises:

Methane Gas and Air Flow Controls

For each gas there are two controls an On/Off valve and a needle valve on the bottom of the flowmeter. These allow for control of the flows of air and methane passing to the burner unit and need to be set correctly to provide a gas mixture suitable for ignition. See the NES 713 standard for size and type of flame required. It has been found suitable flows are approximately 10-15 litres per minute for the air and 1-2 litres per minute for the methane. Once the gas mixture has ignited then the relative flows can be adjusted to give the flame required.

WARNING

If the gas mixture fails to ignite within a few seconds under the above standard conditions, turn off the gas supply, evacuate the chamber until satisfied that non-hazardous conditions exist and then repeat the ignition cycle and if system still fails to ignite, shut down completely and contact supplier for advice.

Control Switches

These are the five red switches on the front panel. They are operated by firm pressure and light up when activated. A detailed description of the control switches is given below:-

POWER This allows the mains electrical supply through to the control unit electronics. Once this is ON the other control switches can be operated independently.

IGNITIONThis operates an electrical ON/OFF gas valve to allow methane gas to pass from the gas flow control unit to the burner unit. Simultaneously an ignition unit is activated which generates a spark at the top of the Bunsen burner. This will ignite the gas provided the mixture is correct. (see WARNING above).

FANThis operates the mixing fan mounted inside and at the top of the Combustion Chamber. The fan mixes the combustion products inside the chamber to prevent the heavier particles settling to the bottom whilst the gases are undergoing analysis.

VENT This opens the exhaust vent mounted in the roof of the combustion chamber to allow removal of combustion products from the chamber by the extraction motor.

EXTRACTION This operates the Extraction motor mounted on top of the Combustion Chamber and extracts smoke from the chamber provided the vent is open.

TIMERThis timer is continuous and is reset by pressing the button. It is powered by an internal lithium battery which has an expected life of 8 years.

WARNING

The chamber must be connected to a suitable external extraction system to ensure combustion products are vented to a safe area.

Figure 2.8: Combustion Control Unit

Gas Analysis

For analysis of the gases the unit is supplied with a metering pump of capacity 100ml for use with the colorimetric gas detector tubes. 1 box of each of the 14 gas detector tubes needed to carry out the NES 713 test analysis is supplied (except for Acrylonitrile where two boxes are provided).

Note:In order to minimise losses of certain toxic products through adsorption, condensation, etc, prior to measurement, all sampling lines shall be as short as possible

3. Test Procedure

Introduction

The Defence Standard 02-713 Issue 2 gives the requirements for one of a series of test methods for determining the fire characteristics of materials, which are referred to in Def Stan. 07-247.

The latest issue of the standard is available at http://www.dstan.mod.uk

The test explores the toxicity of the products of combustion in terms of a limited set of small molecular species arising when a small specimen of a material is completely burnt under specified conditions. A combined toxicity index is calculated from the test results using the exposure level (in ppm) of each gas to produce fatality in 30 minutes.

The test is intended to form part of the pre-selection screening process for materials and should not be interpreted as an assessment of toxicity hazard under actual fire conditions. The test method is directed at the analysis of a specified set of gaseous species, which are commonly present in combustion products of materials used in military applications and which may cause lethality at the time of the fire. It does not address acute mental incapacitation effects, delayed/long term toxicity, or toxicity involving particulate combustion products. The set of gaseous species analysed is not exhaustive and the test does not necessarily determine the total toxicity of all the constituents of the products of combustion.

The test does not attempt to account for the influence of the rate of combustion of a material on its contribution to toxicity hazard.

General Description Of The Test Method

Small specimens of pre-determined mass (usually approximately 1 gram) are completely burnt inside a sealed chamber of volume 0.7 - 1.0 m3, using a Bunsen burner fed with air and gas to give a non-luminous (blue) flame, having a temperature of 1150 25C.

The resulting chamber atmosphere is quantitatively analysed for a specified set of gases. Background corrections are subtracted for the amounts of carbon monoxide, carbon dioxide and oxides of nitrogen produced by the burner.

For each gas, the measured concentration (Ci) is scaled up for 100 g of material and re- calculated as though the combustion products were diffused into a volume of exactly 1 m3. The resulting concentration (C8) is expressed as a ratio of the Critical factor (Cf), which is equal to the concentration of that gas considered fatal to man for a 30 minute exposure. The ratios (C8/Cf) are summed for all gases detected to give a Toxicity Index (TI) for the material.

Specimen Preparation

Conditioning

Before cutting test specimens from the sample of material, condition the sample to a constant mass at 23C 2C and 50% 10% relative humidity. Constant mass is considered to have been reached when two successive weighing operations, carried out at an interval of 24 hours, do not differ by more than 0.1 % of the mass of the sample or 0.1 g, whichever is the greater (see BS EN ISO 291).

Specimen Size

Cut the specimens to size and store them under the same conditions until required for testing. If the test apparatus is not located in a humidity conditioned laboratory, the test procedure shall be started within 3 minutes after the removal of each test specimen from the conditioning enclosure.

The size and shape of all test specimens shall be such that they are entirely engulfed in the flame during the test.

Where possible, the test specimens shall be cut as a single piece, approximately in the form of a cube.

Note: Each of the test specimens for a material must be of the same size and shape.

Where the sample is a multi-layered sheet, the specimens shall be cut as a cross-section through the full thickness of the sheet, to include a representative proportion of all components/layers of the product.

Once the specimens have been cut from the sample of material, ensure they are handled carefully to avoid contamination.

Specimen Mass

0.000Unless otherwise specified, all test specimens shall have a mass of 1.0000.050 gram.

Specimen masses other than 1 gram may be used if specified by the technical authority named in the tender or contract in which this Def Stan. is specified, or by any relevant material specification.

For low density materials (e.g. foams) for which a 1 gram test specimen would be too large to be engulfed in the burner flame, then reduce the size/mass of specimens, to ensure that this can be achieved. Use the largest possible specimens that will allow this requirement to be met.

Also, if any of the gases give an indication that exceeds the maximum scale reading on the colorimetric tube for that gas, then it is permissible to reduce the size/mass of specimens in order to achieve a reading within the available maximum range. When this is necessary, discard all of the results obtained using the original (higher mass) specimens and carry out all of the determinations (including the measurement of all gases) in the same runs, using this reduced specimen mass.

If specimens of the size determined above are found to burn for longer than 2 minutes or if pressure in the chamber exceeds 50 mbar (whichever occurs first), then pressure inside the chamber can become unsafe. In such cases, stop testing at 2 minutes, and do not conduct gas analysis. Evacuate the chamber and repeat the test with a smaller specimen size/mass, to ensure that they are completely consumed in less than 2 minutes and the pressure in the chamber stays below 50 mbar.

FTT recommends that tests are performed without colorimetric tubes to determine the specimen mass required to achieve all of the above criteria before conducting the full toxicity analysis. This may mean reducing the sample size until the above criteria are met.

If any dripping or spitting of the sample occurs during the test, then glass wool or wire shall be used to support the specimen. See 10 of Section 3.5.

Number Of Test Specimens

A minimum of two test specimens are required in order to obtain at least two determinations for each gas.

Measurement Of Flame Temperature

At the start of each testing day set up the burner as follows.

1) Ensure that the air temperature in the chamber is 23 2C.

2) Position the burner in the centre of the test chamber floor, without the specimen support in place. The chamber door will need to be open during this procedure.

3) Turn on the air by using the On/Off valve and adjust the flow rate to 10-15 l/min

4) Ensure that the Fan, Vent and Extraction buttons are off and that the Power button is On.

5) Open the Methane On/Off valve and then press the Ignition button. Adjust the maehtane gas flow as required to allow the burner to ignite.

6) Adjust the flow rates of gas and air to achieve a non-luminous (blue) flame 100 mm to 125 mm in height (measured to the tip of the outer blue cone), having a temperature of 1150C 25C at its hottest point, measured with a thermocouple.

7) Record the flame temperature, T(C), at its hottest point and note the position of this hottest point (distance from the floor of the chamber). Also record the flow rates of the gases.

8) Close the chamber door and tighten the clamps. Firmly put the inlet vent plug into the lower left side of the chamber.

9) Press the Vent button to close the exhaust vent and check that the flame temperature is still within 1150C 25C. If not then repeat steps 6 9.

Within 2 minutes or 50 mbar of chamber pressure, extract the chamber by pressing the vent and extraction buttons.

10) Press the Ignition button and turn the two On/Off valves to the Off position to extinguish the burner.

Note: It is best to use the clamp stand to hold the thermocouple in the flame. In this way the burner can be moved away in order to measure the height from the chamber floor to the thermocouple.

Specimen Test

1) Ensure that the apparatus is clear of combustion products from any previous test.Between test runs, clean the specimen support to ensure that no residue remains. Also clean the interior walls of the test chamber and all apparatus inside the chamber, as necessary to remove any sooty deposits.

Note: This is important to avoid cross contamination between different specimens/materials and to prevent the build up of sooty deposits on the inside of the chamber, which may absorb gaseous combustion products.

WARNING

Even after venting, when the apparatus is apparently clear of combustion products, the contaminants remaining inside the chamber may be hazardous (e.g. respiratory, skin, eye). Note also that the apparatus may still be hot (e.g. burner and support frame). Appropriate protection measures shall be taken to prevent exposure of the operator.

2) Ensure that the air temperature in the chamber is 23 2C.

3) Select a test specimen and determine its mass in grams to 3 decimal places.

4) Place the test specimen on the support, approximately in the centre of the test chamber floor. Adjust the position of the support so that the specimen will be sited within the flame boundary at the hottest point established in Section 3.4 so it will be subjected to the a flame temperature of 1150C 25C.

For materials that would otherwise melt and/or drip, test specimens may be supported on a thin bed (single layer, approximately 0.02 g) of glass wool, placed on the wire mesh support to prevent losses during the burn. The use of glass wool shall be stated in the test report. Use a fresh piece of glass wool for each specimen.

For low density materials (e.g. foams) that are liable to be displaced/blown by the force of the gas flame, it is permissible to hold the specimen in place on the support using a loop of wire (for example Nickel-chromium alloy wire, 0.5 - 0.6 mm in diameter). In doing so, do not crush or otherwise distort the test specimen. The type of wire used shall be stated in the test report.

5) Prepare the colorimetric gas reaction tubes by breaking off the end sealing parts, for the gases to be measured, and connect each tube to a separate gas sampling port INSIDE the chamber. Use a new short length of silicone tubing to connect the tube to the sampling port and observe the direction of flow on the colorimetric tubes.

Each sampling port that has a colorimetric tube connected to it must be blanked off on the outside of the chamber by tying off a short length of silicone tubing (as shown in Figure 3.1)

Any ports not used must be sealed by either linking adjacent ports with a loop of silicone tubing, or by tying off a length of silicone tubing. As an example the photo in Figure 3.1 shows the chamber prepared with 10 out of the 12 ports being used and the top right port with a tied off length of silicone. The two ports linked together in the photo are not being used.

Figure 3.1: Sampling Ports

6) Ensure that the Fan, Vent, Extraction and Ignition buttons are off and then close the test chamber door and tighten the clamps. Then firmly insert the inlet vent plug in the lower side of the chamber.

7) Then turn on the air On/Off valve. (Note that the exhaust vent is still open)

8) To start the test, turn on the gas On/Off valve, press the Ignition button and the Vent button simultaneously and start the timing device.

WARNING

For safety reasons, if the burner does not ignite within a few seconds, turn off the gas and air supplies and evacuate the chamber (push Vent Off and push Extraction On). This is to avoid the build up of un-ignited gas in the chamber. Re-adjust the burner settings to achieve ignition and carry out a repeat test.

9) Throughout the test, make observations of the behaviour of the specimen and note the times at which the observations were made, including whether or not the specimen ignites, plus other behaviour such as charring, melting, dripping, shrinkage, intumescence, fragmentation, explosive decomposition/spitting, erratic burning, after- glow, or any loss of material from the specimen.

10) If any material is lost from the specimen during the test (e.g. by dripping or spitting) or the specimen moves, so that any part is no longer within flame boundary, then the test shall be halted and the results discarded. A repeat test shall be carried out with a fresh specimen, using glass wool or wire to support the specimen.

11) The duration of the burn is to be sufficient to ensure that all of the combustible material within the specimen is completely consumed.

During a test run, while gas and air are being fed to the burner, there is likely to be an increase in the pressure inside the test chamber because it is sealed. It is important not to continue to run the burner for longer than 2 minutes or exceed 50 mbar of pressure, as this pressure build up may cause the chamber to leak and/or may be dangerous. It is therefore important not to use oversize test specimens (see Section 3.3.3), which may take longer to be completely burnt.

Note: Even for the same material, from specimen to specimen there may be small variations in the time taken for combustion to be complete. It is therefore recommended in the first run, to continue the burn after all signs of combustion of the specimen have ceased, up to the next increment of 15 seconds, to allow for the possibility that subsequent specimens may burn for slightly longer. Typical burn times are therefore 60 s, 75 s, 90 s.

12) When the burn is judged complete, extinguish the burner by turning the methane and air On/Off valves Off and push the Ignition button. Record the time as the burn time, tburn (seconds). The same burn time shall be used for each of the subsequent specimens tested for the same material.

Note: If the material does not ignite or show any other signs of production of gases from the specimen in the first 60 seconds of the burn, stop the run at 60 seconds, as described above and continue the procedure using this as the burn time (i.e. t = 60 seconds). This behaviour shall be recorded in the test report.

13) Immediately start the mixing fan (push the Fan button On) and continue mixing for 30 seconds, then switch off the fan (push the Fan button Off).

14) Then immediately commence sampling the atmosphere from the chamber by drawing the gas mixture through the sampling ports using the supplied metering pump. Use a short length of silicone tubing to connect the sampling port to the metering pump. Some notes on the use of colorimetric tubes are given in Section 3.7.

Analysis for halide gases must be carried out first, in order to minimise potential losses through adsorption, condensation, etc, which may be experienced through a delayed estimation.

The preferred order for sampling is as follows:

(i) HF: Hydrogen fluoride(ii) HCl: Hydrogen chloride(iii) HBr: Hydrogen Bromide(iv) C6H5OH: Phenol(v) SO2: Sulphur dioxide(vi) H2S: Hydrogen sulphide(vii) HCN: Hydrogen cyanide / Hydrocyanic acid(viii) CH2CHCN: Acrylonitrile(ix) HCHO: Formaldehyde(x) CO: Carbon monoxide(xi) CO2: Carbon dioxide(xii) NOx: Nitrous fumes(xiii) NH3: Ammonia

Sampling of gases must be completed within 25 minutes of the end of the burn period.

15) On completion of the analysis, clear the remaining products of combustion from the chamber push the Vent button Off, then the Extraction button On.

Note:The room exhaust system must be switched on and connected to the outlet of the extraction pump on the instrument.

16) After 30 seconds or when the chamber pressure is below 5 mbar, remove the inlet vent plug from the lower left side of the chamber.

17) When all the smoke is removed from the chamber then open the chamber door, replace the inlet vent plug and push the Extraction button Off.

WARNING

Even after venting, when the apparatus is apparently clear of combustion products, the contaminants remaining inside the chamber may be hazardous (e.g. respiratory, skin, eye). Note also that the apparatus may still be hot (e.g. burner and support frame). Appropriate protection measures shall be taken to prevent exposure of the operator.

18) Examine the residue of the test specimen to ensure that all of the combustible material has been consumed. If any portion of the combustible material remains unburnt or appears to be, discard the results and carry out a repeat test run using a fresh specimen and a longer burn time (or if necessary using a smaller specimen).

19) After the first specimen burn, carry out a determination of the background (burner) corrections (see Section 3.6).

20) Repeat steps 1) to 18), with fresh specimens, using the same burn time and specimen form, for as many times as necessary to obtain at least two consistent determinations for each gas.

Note:It may be necessary to reduce the specimen mass if gas concentrations exceed the measurement range of the colorimetric tubes.

21) After the last specimen burn carry out a further determination of the background (burner) corrections (see Section 3.6).

22) The whole procedure can then be repeated for the next sample.

Background Correction Procedure

The carbon monoxide (CO), carbon dioxide (CO2) and nitrous oxides (NOx) concentrations measured after a test require correction to remove the background concentrations of these gases resulting from the burner.

Two determinations of the background (burner) correction are conducted, one after the first specimen burn, in which the burn time is established and another after the final specimen burn. The background concentration of each gas is taken as the average concentration of the two determinations

If more than one material is tested during a working day, using the same burn time, then it is permissible to use the same background corrections, provided the burner flow rates and gas supply pressures are unchanged.

1) Ensure that the air temperature in the chamber is 23 2C.

2) With the cleaned specimen support in place, but no specimen in the chamber, place carbon monoxide, carbon dioxide and nitrous oxides colorimetric tubes in position. Use a new short length of silicone tubing to connect the tube to the sampling port and observe the direction of flow on the colorimetric tubes. Ensure that all other sampling positions are sealed. Seal all used ports with a tied off short length of silicone tubing.

3) Ensure that the Fan, Vent, Extraction and Ignition buttons are off and then close the test chamber door and tighten the clamps. Then firmly insert the inlet vent plug in the lower left side of the chamber.

4) Then turn on the air On/Off valve. (Note that the exhaust vent is still open)

5) To start the test, turn on the gas On/Off valve, press the Ignition button and the Vent button simultaneously and start the timing device.

WARNING

For safety reasons, if the burner does not ignite within a few seconds, turn off the gas and air supplies and evacuate the chamber (push Vent Off and push Extraction On). This is to avoid the build up of un-ignited gas in the chamber. Re-adjust the burner settings to achieve ignition and carry out a repeat test.

6) After tburn seconds extinguish the burner by turning the methane and air On/Off valves Off and push the Ignition button.

7) Immediately start the mixing fan (push the Fan button On) and continue mixing for 30 seconds, then switch off the fan (push the Fan button Off).

8) Then immediately commence sampling the atmosphere from the chamber by drawing the gas mixture through the sampling ports using the supplied metering pump to determine the concentrations of carbon monoxide, carbon dioxide and nitrous oxides. Use a short length of silicone tubing to connect the sampling port to the metering pump.

9) On completion of the analysis, clear the remaining products of combustion from the chamber push the Vent button Off, then the Extraction button On.

Note:The room exhaust system must be switched on and connected to the outlet of the extraction pump on the instrument.

10) After 30 seconds or when the chamber pressure is below 5 mbar, remove the inlet vent plug from the lower left side of the chamber.

Use Of Colorimetric Gas Reaction Tubes

Once combustion of the specimen is complete and after stirring, a controlled volume of chamber atmosphere is drawn through the colorimetric gas reaction tubes via sampling ports.

Unique tube types are provided for each gas, which contain indicator chemicals that have a specific reaction with the particular gas, leading to a colour change. The length of the resulting colour indication is measured against a printed scale on the side of the tube that gives a direct reading of the concentration of the gas.The metering pump provided draws 100 ml of gas through the tube per press of the bellows (stroke) and each tube indicates the number of strokes required.

Follow the instructions given by the manufacturer of the tubes for reading the length of the colour indication against the scale graduations. In addition:

a) Readings in between the graduations may be estimated visually, noting that the scales on some types of tube are not linear.b) However, if there is a colour indication at the start of a tube which does not reach the lowest graduation on the scale, use zero as the value of the concentration, Ci, for that determination of the gas.

The tubes must be positioned within the chamber itself, in order to minimise losses through adsorption, condensation, etc. The outside of each port that is in use must be tied off as detailed in (5), Section 3.5

It is known that for some gases the stain in the indicator chemicals can fade in a relatively short period of time. These tubes shall be read as soon as possible after the gas sample has been drawn through them, hence the recommended order for sampling given in Section 3.5 Step 14 (For example, one type of tube for the measurement of ammonia has been known to exhibit this behaviour).

3.7.1 Measurement of Hydrogen Bromide (HBr) Using Colorimetric Gas Reaction Tubes There are currently no colorimetric gas reaction tubes available that are specifically designedto measure hydrogen bromide (HBr). However, some types of tube that are designed for measurement of other gases, are known to give a reading in the presence of HBr, although with a different measurement sensitivity.

The hydrochloric acid tube supplied will give a reading in the presence of HBr, but with a measurement sensitivity from approximately 1 to 0.3 times that for HCl.

The procedure is shown schematically overleaf in Figure 3.2.

If this tube gives a zero reading, this may be taken to indicate that HBr (as well as HCl) is not present in the combustion products.

When this tube gives a non-zero reading, it is necessary to distinguish whether the reading is due to HCl, or to HBr, or to a mixture of both of these gases.

This may conveniently be achieved by undertaking a separate elemental analysis of the material under test. The Lassaigne sodium fusion test is a cost effective and convenient method that has been used for this purpose, but other analytical techniques may be used. This will determine whether or not the material contains bromine (Br) and therefore whether its combustion products could contain HBr.

If the material does not contain Br, then the reading on the tube is due to HCl only and the value indicated on the tube can be used in the normal way, directly as the concentration (Ci) of HCl in the test chamber.

If Br or both Br and Cl are present in the material, then the least favourable case (highest possible value of C8) would be given by treating the reading on the tube as if it were all due to HBr. HBr has the lower Cf value (Cf (HBr) = 150, Cf (HCl) = 500) and the tubes are up to (approximately) three times less sensitive to HBr, than they are to HCl, for which the scale on the side of the tube is calibrated. It is therefore necessary to divide the concentration value indicated on the tube by 0.3 and use the figure obtained as Ci, for HBr, to calculate a value of C8 for HBr in Section 3.8 Step 2). A worst case Toxicity Index contribution (C8/Cf) is then calculated using the Cf value for HBr (Section 3.8, Step 4)).

Analysis of combustion products using hydrochloric acid tube

Tube reading = 0

Ci(HBr) = 0Ci(HCl) = 0

Tube reading > 0

Lassaigne analysis of sample

Negative for Br

Ci= tube readingCf = Cf(HCl) = 500

Positive for Br

Ci= tube reading divided by 0.3Cf = Cf(HBr) = 150

Figure 3.2: Example Of Process For Measurement Of Hydrogen Bromide (HBr) Using Supplied HCl Colorimetric Tube

Calculation of Toxicity Index

From the test results the Toxicity Index for the sample is calculated as follows:

1) Subtract the respective background (burner) corrections, determined in Section 3.6, from the carbon monoxide, carbon dioxide and nitrous oxides concentrations measured in the chamber for each test run to give the actual values resulting from combustion of the test specimen.

2) For each determination, use the equation given below to calculate (in ppm) the concentration of the gas, produced under the conditions of the test, scaled up for 100 grams of material and re-calculated as though the combustion products were diffused into a volume of 1 m3 using equation (1):

C Ci 100V8m

(1)

where,Ci = concentration of gas i in test chamber, resulting from combustion of the test specimen (ppm)m = mass of test specimen (g)V= volume of test chamber (m3)

3) Calculate the average value of C8 (in ppm) for each gas.

4) Calculate the Toxicity Index (TI) from equation (2):

TI

C81

C82

C83

C8n

(2)

ffffCCCC123n

where,1, 2, 3,,n represent each of the n gases detected;

iC8 = the average value of C8 for the gas i calculated in step 3) above (ppm);

fC= concentration of the gas i considered fatal to man for a 30 minute exposure timeiValues of Cf are given in Table 3.1 (ppm).

GasCf (ppm)

Carbon dioxide (CO2)100 000

Carbon monoxide (CO)4000

Hydrogen sulphide (H2S)750

Ammonia (NH3)750

Formaldehyde (HCHO)500

Hydrogen chloride (HCl)500

Acrylonitrile (CH2CHCN)400

Sulphur dioxide (SO2)400

Nitrous Oxides (NOx)250

Phenol (C6H5OH)250

Hydrogen cyanide (HCN)150

Hydrogen bromide (HBr)150

Hydrogen fluoride (HF)100

Table 3.1: Cf values

Test Report

The test report shall include a reference to Def Stan 02-713 Issue 2, together with the following information:

a) the name and address of the laboratory undertaking the test;

b) the name and address of the supplier and where different, of the manufacturer of the material tested and the sponsor of the test;

c) the date(s) of the test;

d) a full description of the material tested, including; commercial name, including any unique identification number or grade reference batch number laboratory sample reference number/code NATO stock code no. material or product specifications to which the material complies (e.g. Def Stan.BS, etc) application (e.g. deck covering, thermal insulation, etc) material type (i.e. generic description of the chemical nature or composition e.g.wood, EPDM rubber, mineral wool, etc) type of product (i.e. form or shape e.g. sheet, pipe/tube, coating, foam, moulded shape, fabric, etc) essential dimensions (e.g. mass or density, sheet size/thickness, layers, etc.) colour (in the case of paints/coatings the finish coat surface colour)

coatings details (e.g. temporary substrate used to produce free films, application method (brush/spray), no. of layers, coverage rates, thicknesses, etc.) details of any previous test known other relevant information about the sample, useful in identifying the materialtested

e) a full description of the specimens tested, including approximate shape and dimensions and the location and orientation from which the specimens were taken in relation to the sample and any inhomogeneity of the material (e.g. surfaces, edges, layers, machine directions, multiple phases, etc);

f) whether the specimen was supported on glass wool or held with wire and type of wire used;

g) the analytical method and the calibrated measurement range, used for each gas;

h) the volume of the test chamber, V;

i) the burn time, tburn;

j) the flame temperature, T and gas used (i.e. methane or natural gas);

k) the individual and average values for the background corrections for carbon monoxide (CO), carbon dioxide (CO2) and nitrous oxides (NOx);

l) for each valid determination, values of m, Ci, C8

m) for each gas detected, the average value of C8 and C8Cf ;

n) the Toxicity Index (TI) of the material (per 100g) rounded to 1 decimal place;

o) observations of the burning behaviour of the specimens and the times at which the observations were made, together with reasons for any invalid tests;

p) a note of any possible cross reactions of the colorimetric gas reaction tubes;

q) a note of any deviations from the standard protocol, such as the use of reduced size specimens;

r) the statement: "This test result alone does not assess the fire hazard of the material, or a product made from this material, under actual fire conditions. Consequently, the results of this test alone are not to be quoted in support of claims with respect to the fire hazard of the material or product under actual fire conditions.

NOTES

Should any errors or omissions be found in this users guide or should you require any further information, please contact Fire Testing Technology Limited. Telephone: +44 (0)1342 323600 or Fax: +44 (0)1342 323608.

Appendix A:Spare Parts Price List

The spare parts list for the NES 713 Apparatus is given in the following pages. Please contact FTT or their agents if there are any spares items not included on the list that you require or for prices.