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FAQs for conducting UN Test Series 6(c)

The following ‘frequently asked questions’ are an interpretation of the UN Manual of Tests and Criteria requirements. You must comply with the Manual at all times. However, if any deviation from the requirements is needed, you should seek agreement from HSE before starting the test(s).

If you need to contact HSE about a specific aspect of your test, send your query, by email, to cad.explosives@hse.gov.uk, giving all relevant details.

Frequently asked questions

How much product is needed?

Packages where the volume is less than 0.05m3 to 0.15m3 divided by package volume (answer rounded up to nearest whole number) gives the required number of packages.

For transport packages with a volume greater than 0.05m3, three transport packages will be required.

For small packages, where each is less than 0.05m3, their combined volume is not to be less than 0.15m3, or three packages if each is over 0.05m3.

Do I need to show how the products are packed?

Ideally this would be drawings, but sometimes photographs are acceptable. Video evidence or still photographs should show how the boxes are packed. The evidence should match the packaging specification quoted.

What orientation should the boxes be in?

The boxes should be orientated in such a way that any projections would hit the witness screens.

It is a good idea to mark a double headed arrow on the outside of the transport package indicating the orientation of the devices within; these arrows should point to the witness screens.

How many cameras do I need?

Ideally two high-speed / good quality imaging colour video cameras should be used; one showing a close-up view and one wide-angle view. Make sure the view of the test is not obscured by the witness screens. When positioning the cameras, consider the wind direction, and whether the test results may be obscured by smoke etc.

What should be the format of the film footage?

Many video formats can be used (eg computer formats such as AVI, MPEG, WMV or DVD formats such as PAL and NTSC) but it would be wise to check that the classification Competent Authority can use the proposed formats before starting the tests. For UK, the video format should be ‘PAL’.

Do I need to keep a record of the tests?

Yes. HSE does not keep the records and you may need to produce them at any point during the product’s life.

Should I edit the film footage?

Editing the footage together to include as much information as possible (such as packaging information, orientation of boxes etc) to allow ease of viewing is recommended. However, don’t remove important data or alter the data. You can edit the footage, but it must show the relevant test materials activating. You should keep an unedited copy of the film footage for reference.

Do I need to use the type of fire prescribed in the UN Manual of Tests and Criteria?

As long as the method and materials of the fire meet the spirit of the Manual of Tests and Criteria, both in terms of temperature and burning time, the test results should normally be acceptable. However, you may wish to consult HSE before undertaking a potentially expensive test.

The filmed results of the bonfire test must be able to be assessed by the classification Competent Authority, so a test method which involves dense smoke may not allow sufficient assessment of the product functioning.

The Manual of Tests and Criteria list several different types of methods of burning:

  • Diesel troughs: These are not recommended as the black smoke produced can obscure the test
  • Wood: This is the best option based on price. The fire does not necessarily have to be of the same specification as written in the Manual of Test and Criteria. However, the fire must be large enough to engulf all the packages and burn long enough to consume all the packages and devices. Wooden pallets or scrap wood may be used so long as the burning criteria are met
  • Gas: This is also better than diesel and very controllable, however, this method is a very expensive system

How long does the fire need to last for?

Generally, the fire should burn effectively for at least 30 minutes, but it should burn long enough for all of the test items to activate.

How do I interpret the film footage?

The results seen on the film should be used in conjunction with the assessing criteria of the Manual of Tests and Criteria to assign hazard division.

You should provide a report that gives a short written account of the main features/observations of the test.

What should the film footage show?

The footage should clearly show the method of packaging, set up of the test including orientation of the packages, any marks or indents on the witness screen before and after the test, the initiation of the fire, all of the test items activating, the aftermath of the test, and ideally should have a time-base superimposed.

Can I secure the boxes?

Yes. If necessary, a steel strip may encircle the packages to hold them close together on the burn table, but the strip should not interfere with or prevent the test articles operating, or otherwise give a false result.

How do I transport the samples to the test site?

If the test items are to be transported to a test site by road in Great Britain, you will need to apply to HSE for a ‘Samples Explosives’ classification for the items ahead of the test. You will need to consult with the classification Competent Authority well in advance of the test if you are likely to need this classification.

Does the testing site need to be licensed in any way?

Normally it doesn’t need an explosives licence, but if it is located within, or close to, an existing licensed explosives area’s Red Line, it might need a licence. Check with the relevant HSE inspector for that site.

Are there any weather restrictions?

For both site safety and film analysis, there should be clear visibility. If the wind speed is above 6m/s (13mph) the heat from the fire may not activate all of the test items, and such conditions should be avoided.

Do I need witness screens?

Yes. However, if you are sure that the test items (or their packaging) will not produce fragments, witness screens may not be required. Seek advice from HSE before testing starts.

What if the products don’t all go off?

You may need to repeat the test, particularly if the fire didn’t burn for long enough. Extreme care should be taken with the unexpended items, as their condition is unknown, and they should be destroyed in situ.

Do I need blast / radiometers measuring gauges?

Ideally, yes. However, if you are sure that the test items will not produce violent event, blast metres or radiometers are not required. You may need to justify this to HSE through calculation of the thermal flux values for the energetic material(s) undergoing test.

How can I get further help?

Further advice and help can be sought from:

Updated 2012-12-17