FlameOut Breathe FR breather membrane

SafeOne Class A Installation

Safe One® breather membrane

SAFE ONE® is a Class A2 rated breather membrane, independently tested to EN 13501-1.

Breather membrane Euroclass rated A2,s1-d0 for walls and roofs

  • Compliant with UK Building Regulations Approved Document B
  • Superior W1 water resistance
  • Vapour permeable
  • High UV resistance
  • Independently tested for compliance
Installation Instructions
Technical Briefing
UK Building Regulations
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Safe One Flame Retardancy Test
Safe One Whitepaper

Euro Class System –
Flame Retardancy

Fire Behaviour

  • A1 = noncombustible
  • A2 = very limited combustibility
  • B = combustible (limited)

What functions do breather membranes provide?

Breather membranes are used in roof and wall installations to ensure long-term protection to the building envelope. Breather membranes offer water repellent properties combined with high water vapour permeability to  control condensation within the building’s interior. Specialist breather membranes with additional characteristics, such as  high UV resistance, ventilation control and energy efficiency, are also beneficial  for the building’s long-term protection.

Breather membranes perform various key functions. Firstly, they allow the easy release of excess moisture vapour into the atmosphere. This functions keeps the internal wall/roofing structures dry.  Secondly, breather membranes protect against the ingress of dirt, dust and rain which are especially problematic when coupled with driving rain. Some systems also provide protection against the impact of solar light and heat.

Breather membranes must perform these protective functions without compromising their breathable qualities. Breather membranes are installed between the insulation and the outer wall layers (e.g, cladding or roof tiles). If they protect from external conditions without being sufficiently  breathable, the naturally occurring moisture within the building will be trapped in the interstitial layers. This will be highly damaging in the long term.

Flame retardant standards for breather membranes

British and international building standards specify flame retardant materials for specific installations and structures. Flame retardant additives are incorporated within the materials or added as a coating to make them flame retardant; it is the formulation, quality and amount of these additives that determine which flame retardant tests the material will pass and what standards to which they will comply.

A flame retardant material is one that self-extinguishes; it does not mean that it is flame proof. Flame retardant materials are resistant to catching fire, reduce flammability, and inhibit, suppress or delay the production of flames. Flame proof materials are ones that are not liable to catch fire or be damaged by fire and are not readily ignited or burned by flames.

In 2002, to harmonise the classification of the reaction to fire for building materials, the European Commission introduced the Euro Fire Class System (Euroclass) based on EN ISO 13501-1. 

Current regulations require an external wall construction over 18m to have a minimum Euroclass A2-s1,d0 fire safety rating. However, breather membranes are currently exempt from being part of an A1 or A2-s1, d0 vertical wall system; they are required by law a minimum Euroclass rating of B,s3-d0. In Scotland, this requirement applies to external wall constructions over 11m.

Following the introduction of the Building Safety Act in 2022, the latest regulations are subject to ongoing review and the construction industry should plan for further regulatory change. Best practice recommends the use of breather membranes which have a Euroclass A2-s1,d0 fire safety rating in line with the requirements for cladding and other external wall materials.


EN 13501-1

Fire classification of construction products and building elements. Classification using test
data from reaction to fire tests (EU).

BS 476

PART 6 Fire tests on building materials and structures. Method of test for fire propagation for products (UK)

BS 476

PART 7 Fire tests on building materials and structures. Method of test to determine the classification of the surface spread of flame of products (UK

Euro Fire Class System and National Fire Class Systems*

Euro ClassEN ISO 13501-1 UKBS 476 Parts 6 & 7 GermanyDIN 4102
Class A1 NA A1
Class A2 Class 0 A2
Class B Class 0 B1
Class C Class 1 B1
Class D Class 1 B2
Class E Class 2 B2
Class F Class 3 B3

*Indicative purposes only; test methods and standards vary



Class A1 – non-combustible
Class A2 – very limited combustibility
Class B – combustible (limited)
Class C – normal flammable
Class D – normal flammable
Class E – normal flammable
Class F – not classified materials


Class S1 – very limited smoke
Class S2 – limited smoke
Class S3 – no demands on smoke


Class d0 – no droplets or particles
Class d1 – limited burning droplets
Class d2 – no demands on droplets

Non-combustible building materials

A1 or A2

Highest level for flame retardant materials

B-s1, d0

Flame retardancy tests for breather membranes

To meet the requirements for EN ISO 13501-1, the Euro Fire Class System, two test standards must be passed.

EN 11925-2

Single Flame Source Test “Reaction to fire tests for building products— Part 2: Ignitability when subjected to direct impingement of flame.” The method specifies a test for determining the ignitability of products by direct small- flame impingement under zero impressed irradiance using vertically oriented test specimens.

Although the method is designed to assess ignitability, this is addressed by measuring the spread of a small flame up the vertical surface of a specimen following application of a small (match-sized) flame to either the surface or edge of a specimen for either 15sec or 30sec. The determination of the production of flaming droplets depends on whether or not the filter paper placed beneath the specimen ignites.

Pass standard:

  • Flame spread (Fs) <150mm within 60sec (when exposure time is 30sec)

EN 13823

(SBI) Single Burning Item (SBI) Test “Reaction to fire tests for building products—Building products excluding floorings exposed to the thermal attack by a single burning item.” A method of test for determining the reaction to fire behaviour of building products (excluding floorings) when exposed to the thermal attack by a single burning item (a sand-box burner supplied with propane). The specimen is mounted on a trolley that is positioned in a frame beneath an exhaust system. The reaction of the specimen to the burner is monitored instrumentally and visually. Heat and smoke release rates are measured instrumentally and physical characteristics are assessed by observation.

Pass standards:

  • Fire Growth Rate Index (FIGRA) must remain below 120 W/s
  • Total Heat Release (THR) in the first 600sec of exposure must be <7.5MJ
  • Lateral Flame Spread (LFS) must not reach the edge of the specimen, the
    flame spread (Fs) must be <150mm within 60sec

UK Building Regulations for external walls

Building regulation in England covering fire safety matters within and around buildings are specified in Approved Document B (Fire Safety) Volume 1 (dwelling houses) and Volume 2 (buildings other than dwelling houses). The documents specify the minimum standards (BS 476 and EN ISO 13501-1) for all materials used in the construction, with specific installation requirements. The full document is available online: www.gov.uk.

Single Flame Source Test apparatus for EN 11925-2

Single Burning Item Test apparatus for EN 13823

UK Building Regulations Update

On 21 December 2018, changes to the Building Regulations 2010 specified that materials used in the external walls of buildings over 18m must now be Class A1 or A2, as determined by EN 13501-1. This relates to buildings containing dwellings, institutions or rooms used for residential purposes. Class 0 rated materials (as determined by BS476 Parts 6 & 7) no longer qualify. Materials excepted include: door frames and doors, fire stopping materials, membranes, seals/gaskets/ fixings/sealants and thermal break materials.


SAFE ONE® is a limited combustible breather membrane, independently tested to EN 13501-1.

FLAMEOUT® BREATHE membrane is breathable, non-woven fabrics with superior self-extinguishing, flame retardant properties, available in two grades of FR rating. It is independently tested to EN 13501-1 and is suitable for wall and roof installations.

FLAMEOUT® VCLs are polyethylene-based vapour control membranes with a reinforcement scrim to provide sufficient tensile strength in wall and roof insulations. They are independently tested to British and international flame retardant standards. Air and Vapour Control Layers (AVCLs) ensure that the building envelope is properly sealed to control ventilation and prevent heat loss in compliance with Building Regulations Part L. Installed on the warm side of insulation, AVCLs protect insulates from interstitial condensation.


Flame Retardant




Tensile strength

Temperature range

Water vapour resistance

Water vapour transmission

Resistance to Penetration of Air

Water tightness


Roll weight

Pallet quantity

FlameOut Breathe

Class B-s1,d0

Dark grey



MD 170 XD 140

-40/ +70

0.1 MNs/g

Sd 0.02m EN ISO 12572 BS 4016 Class 1



1.5 x 50 3.0 x 50

7.2 14.0

28 28

Safe One (SF400)*

Class A2-s1,d0


Openings <50mm Overall exposure not to exceed 50% of the surface area


MD 1400 XD 1400


0.6 MNs/g

Sd 0.12m EN ISO 12572



2.65 x 20



FlameOut Block

Class B-s1,d0

Milky White



MD>500 XD>500


140 MNs/g

Sd 28m EN 1931 1.56 g/m2/day BS 3177



2 x 50



FlameOut Block Plus

Class B-s1,d0

Milky White



MD>500 XD>500


300 MNs/g

Sd 60m EN 1931 0.77 g/m2/day BS 3177



2 x 50



FlameOut Block Class A A2-s1,d0 White/Silver NA 155 MD>1,200
XD >1,000
20,000 MNs/g Sd 4,000m NA W1 1.5 x 50 13.5 27

NOTE: As per EN 13859-2, Clause 5.2.2, in the case of the breather membrane being used on a supporting structure, further flame retardant testing of the structure may be needed to determine the flame retardancy of the construction due to a possible different flame retardancy of the supporting construction ma- terials itself (e.g. wood). The Safe One breather membrane is Class A2-s1,d0 when free hanging or directly installed on a supporting substructure with a flame retardant classification of A1 or A2. The FlameOut Breathe FR breather membrane is Class B-s1,d0 when free hanging or directly installed on a supporting substructure with a flame retardant classification of A1 or A2. FlameOut Breathe has been tested directly installed onto wood as Class D-s1,d0.

*Important: Register your warranty with ITP prior to installation. Separately provided Installation instructions provided by the Safe One Technical Team must be complied with to validate any warranty. Safe One proprietory adhesives, tapes and accessories must be used to validate any warranty.

FlameOut Projects


Get Living Lewisham

ITP FlameOut Breathe breather membrane is being used on another landmark regeneration project in London following the product’s specification at Get Living, a new 649-home scheme from Muse Developments and build-to-rent operator, Get Living PLC.

View all FlameOut projects