The testing of filled aerosols

SPC/Enforcement/126 Version 4

Author Unit/Section: HID CI4B

Target Audience: HID Staff in CI 1-4 (Bands 0-4), Relevant FOD Inspectors


1 The purpose of this SPC is to clarify the legal and practical situation relating to the leak testing of filled aerosols.  It has been updated to take account of the 2009 revisions of ADR as implemented by the Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations 2009 (as amended) (CDG 2009). In addition, the "Aerosol Dispensers Directive" has been fully implemented in UK law.. It also has information that is relevant in relation to COMAH, both in manufacturing and warehousing of these products. Guidance on enforcement is provided. This update clarifies the issues around immersion of aerosols during a water bath test.


2 The majority of aerosols (properly called 'aerosol dispensers') are pressurised with a mixture of butane and propane  or dimethyl ether (DME). In addition the product itself (eg paints, lacquers. lubricants) may contain flammable solvents. Some are pressurised with compressed gases such as air or CO2.

3 Aerosols containing flammable propellants (the majority) or flammable products create fire / explosion hazards even in small numbers and that hazard of course is much greater in the case of large stores of such products. Some sites may be subject to COMAH including at top tier.

4 For both consumer safety and transport safety reasons, regimes to establish initial integrity of filled aerosols have been developed. This SPC discusses these regimes and their legal basis.

5 Some of this advice has been available in other forms for some years. For example OC 278/34 (rev) at para 46 refers to leak testing, but since the 'Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations ' first came into force in 2004, the advice at para 48 is no longer valid. The current version of the regulations is the Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations 2009 (as amended) (CDG 2009).

Consumer Safety

6 Consumer safety matters are not enforced by HSE or LA H&S inspectors, but by Trading Standards departments. Some difficulty has arisen because of this aspect of the subject.

7 The EC 'Aerosols Directive' is a so-called 'optional Directive' and has recently been amended for the second time since its first application. BAMA has published a fact sheet that explains the background.  The UK has now made The Aerosol Dispenser Regulations (SI 2009 No. 2824) which makes compliance with the Directive mandatory from 29 April 2010.

8 compliance with the Directive requires products to be "water bath tested". The updated Directive also allows alternatives to water Bath testing and this is discussed below. Products complying with all the requirements of the Directive are marked with the 'reverse epsilon' symbol (Э).

9 Para 6.2 of the Directive's annex refers to testing of a 'representative sample'. This paragraph applies to the Member States and provides a means for enforcement authorities to check compliance. It does not apply to aerosol manufacturers. It is para 6.1 of the annex that is relevant to manufacturers and this states 'each filled aerosol dispenser shall be immersed in a bath of water….'

10 Testing for the purposes of the Directive has relevance to the transport requirements discussed below.

Transport requirements

11 Aerosol products have a unique UN identification number, UN 1950. European transport rules are based on UN Model Regulations which are transposed into legally binding transport regulations for each mode of transport. For land transport these are ADR for road and RID for rail. The rules set down a range of basic requirements for aerosols in connection with the materials of construction, how they are filled, tested, packed and marked for transport, as well as how they are transported. Those rules are implemented in GB by CDG 2009. ADR and RID are updated every two years and so the GB regulations are also changed. HSE is the enforcement authority. Northern Ireland has equipment regulations.

12 Included in these rules is the need for each aerosol dispenser to satisfy a 'tightness (leakproofness) test'. Details are set out in the schedule to the draft Improvement Notice at Annex 1 Formerly only a water bath test was permitted. Now, subject to competent authority approval, alternative test methods are permitted.

13 The British Aerosol Manufacturers' Association (BAMA) has for many years published a detailed Code of Practice covering all aspects of aerosol production, testing and transport. It has been superseded by the 'BAMA Standard for Consumer Safety and Good Manufacturing Practice' which covers the entire life cycle of the aerosol. The BAMA Standard is updated regularly and the latest version, is you 4 will be launched in late 2010. The most relevant parts of the standard are available to inspectors. BAMA has kindly permitted inspectors access to these documents but they should not be given to anyone outside HSE. The standard can be purchased from BAMA. The BAMA Standard sets out requirements and guidance on how to achieve them. It manufacturers flexibility to document other equivalent methods of achieving the standards. Part of the 'Manufacturing' code (specifically Module 3.4 - Aerosol Integrity Testing) deals with integrity testing of aerosols and includes guidance on operating the hot water bath test. The water bath test was originally intended to check the integrity of the finished pack (the primary hazard of an aerosol in transport is that it is a pressurised container; flammability is a secondary hazard). It also found "gross leakers" which present a safety risk. Many modern filling lines now use check weighing to detect 'gross leakers'.

14 Some problems have occurred in the interpretation of paragraph 5.1.1 of Module 3.4, and in particular to the guidance to that paragraph where alternatives to 'total immersion' are discussed. Note that the concept of 'total immersion' dates back to 1965 (BS 3914) which was revised in 1974 and again in 1991. Since then the Directive and ADR have overtaken the need for the British Standard which has now been withdrawn.

15 It follows that the hot water bath may function in two ways

  • To heat the aerosol dispenser and by total immersion permit the detection of leaks in any part of it.
  • To heat the aerosol dispenser (less than total immersion) but with a separate leak detection process by other means. There are a number of 'instrumental' techniques available for this purpose. The BAMA standard (last sentence of the guidance to para 5.1.1) is clear that any such system must be properly validated and documented. It is not enough to 'partially' immerse the dispensers with no associated leak test.

16 Most aerosols are transported as 'limited quantities' (LQ). Taking advantage of the LQ provisions does NOT remove the need to carry out appropriate leak testing (ADR 3.4.1(f) is the relevant reference). The LQ provisions are described more fully in the CDG manual.

Alternative to water bath testing

17 ADR allows alternatives to water bath testing to be used subject to approval by the competent authority (Department for Transport). The Vehicle Certification Agency Dangerous Goods Office carries out the approvals. Subject to approval of the test scheme, a manufacturer will be able to test aerosols other than by water bath testing. BAMA has submitted a scheme to DfT and manufacturers who adopt it (or an equivalent) are likely to receive approval. Empty cans would have to be pressure and leak tested before filling and all filled aerosols leak tested as specified in ADR. Note that as well as allowing 'heat sensitive aerosols' to be tested at a lower temperature, ADR allows different arrangements for some pharmaceutical preparations containing non flammable gases. Details are in the schedule to the draft Improvement Notice at Annex 1.

18 The water bath alternative does away with the need to heat the aerosols for the purpose of testing in return for stringent quality control on containers and components to guard against the risk of bursting. It also introduces a 'micro-leak' detection requirement to check the quality of the valve crimped on after filling.

19 as noted above, the Aerosols Directive has been updated (and may be become mandatory in UK). It will permit testing equivalent to that permitted by the transport regime.

Action by Inspectors

20 Inspectors should enforce the requirements of ADR by whatever means are appropriate. The legal basis is in the Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations 2009 (as amended) at Regulation 5. This is not a matter that is modified by risk assessment. It is a fundamental requirement. The regulation creates a series of overlapping duty holders, and inspectors should ensure that the duty holder best placed to achieve compliance is targeted.  This will usually be  the manufacturer. Note that testing for the purposes of the Aerosol Dispensers Directive is deemed to comply with ADR, providing of course that it is done properly. See the reference to the Directive in the relevant part of ADR reproduced as part of the schedule to the draft Improvement Notice at Annex 1.

21 A further consideration is that DSEAR risk assessments carried out by operators (whether COMAH or not) sometimes refer to the aerosol manufacturer's testing regime as justification for not classifying warehouses containing aerosols as hazardous areas. Clearly if the products have not been tested for the purposes of ADR or the Directive that risk assessment may not be valid. Inspectors should ask dutyholders to confirm with their suppliers that relevant leak testing, meeting the requirements of the Aerosol Dispensers Directive or ADR, has been carried out. Ideally that confirmation should be in writing and form part of the 'DSEAR assessment file'. If that confirmation is not available inspectors will need to consider whether a duty holder is complying with Regulation 5 of DSEAR and hence, where relevant, a COMAH duty holder is complying with Regulation 4 of COMAH.

22 GB has made the CDG regulations to implement international agreements intended to secure safety in transport by all modes. Many aerosols are transported internationally. For that reason, as well as to ensure the safety in domestic transport, DfT is keen that the relevant standards are applied. 

23  Many manufacturers of aerosols carry out water bath testing of all aerosols either to comply with the Aerosol Dispensers Directive or for transport.

24 Some manufacturers either do some sample water bath testing or do not leak test at all. These aerosols do not comply with the legal requirements for carriage.

25 In some cases inspectors may find that even where water bath testing is carried out the standards are not maintained as they should be to ensure that the testing is fully effective. The BAMA Standard includes 'self check audit' guides and inspectors may find checklist 3.4 useful during inspection.

26 In securing compliance by whatever means, inspectors should allow the dutyholder (ie the manufacturer) the option of following any approved scheme (paragraph 17 above). A draft IN is attached at Annex 1. Inspectors may of course quote other legal requirements where appropriate (such as DSEAR). A substantial investment may be needed so the time allowed for compliance should be realistic.

27 Where leak testing is carried out, but not on a 100% basis, the same enforcement line should be followed.

28 Where a leak testing regime purports to be in compliance but is not thought to be effective (eg significantly different from the BAMA standard) advice should be sought from a process safety specialist.

29 Some concern has been expressed that for steel aerosols residual moisture may cause corrosion which will affect their pressure integrity. A well run leak test regime will ensure that the aerosols are dry before they are packed and shrink wrapped (see BAMA Standard Module 3.4). An alternative water bath testing does away with that concern altogether.

Adding product to pre-charged aerosols

30 Some small scale manufacturers add product such as paint to aerosol dispensers that have been pre-charged with propellant. The Aerosol Dispensers Directive refers to 'filled aerosol dispenser' so the reverse epsilon mark may only be applied where a post-filling test has been carried out. ADR  refers to 'filled aerosol dispenser' so is aligned with the Directive in that respect. In other words, to satisfy ADR 200 a post-filling test will have to be carried out.

31 Where inspectors encounter arguments that post-filling tests are not required (eg because the pre-filled aerosols have been tested) legal and / or process safety advice should be sought.

Use of non-flammable propellants

32 Strictly speaking, the requirements for leak testing apply to all aerosol dispensers. However the leakage of non-flammable propellant is not a safety issue. Furthermore heating such an aerosol will not produce a large rise in internal pressure in the same way as heating an aerosol charged with LPG or DME. It is possible to leak test such aerosols using 'instrumental' means but inspectors may encounter arguments that in these cases it is not necessary. Advice from CI 4 and/or specialist inspectors should be sought in such cases.

Enforcement Management Model

33 Risk Gap Table 2 (multiple casualties may be expected where serious incidents are caused by or exacerbated by aerosols).

Consequence Serious
Likelihood Remote
Benchmark nil or negligible
Risk gap Substantial

34 Table 3: defined legal standard

35 Table 5.1 Initial enforcement expectation: Improvement Notice

36 Table 6 and Figure 4: Dutyholder factors. There are elements of economic advantage to be gained in this matter, but overall these factors will tend to confirm the initial enforcement expectation. In some cases they may allow a letter rather than an IN, but the inspector should be confident that the outcome will be full compliance.

37 Table 7 Strategic factors. Each test in table 7 will confirm that enforcement is appropriate.

Further Information

For further information on the contents of this circular please contact HID CI 4B.

Annex 1 – Draft Improvement Notice

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Updated 2022-08-16