Does an airbag vest replace a back protector?

The standard rates them as separate protector types with separate force limits, and an airbag only provides its rated performance while inflated. Passive armor is doing the work whenever the bag has not deployed, so whether a garment is designed to be worn with or without additional armor is a product-documentation question, not something the level answers.

What does Level 2 mean on an airbag?

In the EN 1621-4 lab test the inflated protector transmitted at most 2.5 kN mean force from a 50 J impact, with no single strike above 3 kN. It is a published lab result under defined test conditions, not a prediction of any individual crash outcome.

Are electronic airbags certified to EN 1621-4?

Not within the strict scope of the 2013 edition, which covers mechanically activated tether systems. Electronic systems are certified through PPE type-examination against adapted versions of the standard's requirements, and a revised edition of the standard is under development.

How fast must a certified airbag inflate?

The standard requires an intervention time — activation plus full inflation — of no more than 200 milliseconds, and the bag must then stay above its minimum operating pressure for at least 5 seconds.

Why are airbag force limits so much lower than armor limits?

The standard sets a much lower allowance for inflatable protectors: airbag Level 2 permits 2.5 kN of mean transmitted force where a Level 2 back protector permits 9 kN. Levels are only comparable within the same standard and body zone, so always read the part number printed next to the level.

Updated 2026-07-18

Airbag vests and EN 1621-4

How wearable airbags are certified under EN 1621-4: the two performance levels and their transmitted-force limits, trigger and inflation-time requirements for tether systems, and what the certification does not cover.

What EN 1621-4 covers

EN 1621-4 is the airbag part of the EN 1621 impact-protector family — the same family that rates the passive foam armor in jackets and suits. Every part of the family shares one core lab test: a guided 5 kg mass is dropped to deliver 50 J of impact energy onto the protector, and a load cell records how much force passes through to the body side. Lower transmitted force means better performance in the test.^[2]^[7]

The published 2013 edition covers mechanically activated systems — airbags fired by a lanyard tethered to the motorcycle. Inflatable protectors are tested in their inflated state, and an airbag only provides its rated performance while inflated.^[1]^[3]^[4]

The two levels and the numbers behind them

Like the other parts of the family, EN 1621-4 defines two performance levels from the same 50 J drop test, measured with the bag inflated.^[1]

Level 1 — at most 4.5 kN mean transmitted force, with no single strike above 6 kN.^[1]^[3]^[4]
Level 2 — at most 2.5 kN mean, with no single strike above 3 kN. This is the lowest transmitted-force allowance anywhere in the EN 1621 family.^[1]^[3]^[4]

For scale, a Level 2 back protector under EN 1621-2 may pass through up to 9 kN in the same test, and Level 2 limb armor up to 20 kN — an inflated airbag is held to a ceiling several times lower than any passive protector.^[1]^[7]^[8] Two cautions belong next to that comparison. First, levels only compare within the same standard and body zone; an airbag Level 2 and a limb Level 2 describe very different numbers, which is why the part number matters as much as the level (see armor levels).^[1]^[7] Second, the kN limits are laboratory comparison values, not real-world crash forces — the standards themselves note that the test forces do not translate directly to the forces riders meet in accidents.^[1]

Tethered triggering, inflation time and the uninflated case

For tether systems, the 2013 edition regulates the trigger itself, not just the cushion.^[1]^[4]

Activation force — between 30 N and 250 N, with activation energy under 5 J.
Connection strength — the bike-to-rider connection must have a breaking strength of at least four times the activation force, and never below 400 N.
Intervention time — activation plus full inflation must take no more than 200 ms, and the bag must then stay above its minimum operating pressure for at least 5 seconds.^[1]^[2]^[4]
Uninflated behavior — hard components of the system must transmit no more than 35 kN even with the bag uninflated.^[1]^[4]

Electronic systems sit at the edge of the standard

Electronic airbags fire from onboard sensors instead of a tether, and they sit outside the strict scope of the 2013 edition, which covers mechanically activated systems only. Systems such as Dainese D-air, Alpinestars Tech-Air, In&motion and Helite e-Turtle are instead certified through PPE type-examination against adapted versions of the EN 1621-4 requirements, and a revised edition of the standard is under development.^[1]^[3]^[5]^[6]

The practical consequence: an electronic vest's label may reference EN 1621-4 even though the product is not strictly within the 2013 scope. That is not a red flag by itself — it reflects a standard whose published scope predates a revision now under development to address electronic systems — but it is worth knowing that the impact levels were assessed against adapted requirements rather than the published tether standard.^[1]^[5]^[6]

What the label shows, and what it cannot

An inflatable protector's label typically shows the standard reference with its edition year and the level achieved. As everywhere in EN 1621, the level is a published lab result for the tested protector, never a promise about a particular crash.^[1] Our label decoder walks through the markings piece by piece.

Several things that matter when comparing airbag products are not answered by the level number:

Coverage. The level describes transmitted force, not how much of the body the inflated bag covers — coverage varies by design and is not encoded in the level.
Re-arming. The standard tests trigger behavior and inflated performance. How a deployed system is re-armed, and at what cost, is answered by product documentation, not the label.
Subscriptions. Any app or subscription requirements attached to an electronic system are likewise outside the standard; product documentation is the place to check.

The honest summary of the category: the lab numbers for inflated airbags are the strongest in the impact-protector family, and the certification framework is still catching up to how these products now trigger. Check the label, read the product documentation for the parts the label cannot cover, and treat the level as what it is — a measured result under defined test conditions.^[1]^[6]

Common questions

Does an airbag vest replace a back protector?: The standard rates them as separate protector types with separate force limits, and an airbag only provides its rated performance while inflated. Passive armor is doing the work whenever the bag has not deployed, so whether a garment is designed to be worn with or without additional armor is a product-documentation question, not something the level answers.
What does Level 2 mean on an airbag?: In the EN 1621-4 lab test the inflated protector transmitted at most 2.5 kN mean force from a 50 J impact, with no single strike above 3 kN. It is a published lab result under defined test conditions, not a prediction of any individual crash outcome.
Are electronic airbags certified to EN 1621-4?: Not within the strict scope of the 2013 edition, which covers mechanically activated tether systems. Electronic systems are certified through PPE type-examination against adapted versions of the standard's requirements, and a revised edition of the standard is under development.
How fast must a certified airbag inflate?: The standard requires an intervention time — activation plus full inflation — of no more than 200 milliseconds, and the bag must then stay above its minimum operating pressure for at least 5 seconds.
Why are airbag force limits so much lower than armor limits?: The standard sets a much lower allowance for inflatable protectors: airbag Level 2 permits 2.5 kN of mean transmitted force where a Level 2 back protector permits 9 kN. Levels are only comparable within the same standard and body zone, so always read the part number printed next to the level.