This part 3 of EN 13138 specifies safety requirements for design, sizing, materials, strength and in-water performance as well as provisions for marking and the information supplied by the manufacturer for swim seats. It also specifies the relevant test methods. This standard is not applicable to products covered by EN 13138-1 and -2. This part 3 of EN 13138 applies only to devices into which the user is placed and which have either inherent buoyancy or can be inflated or a combination of both. It only applies to Class A devices intended to introduce the user to the range to the water environment. These devices are only intended for children aged up to 36 months with a body mass less than or equal to 18 kg. It does not apply to Class B or Class C devices, to pull buoys, swim rings, lifebuoys, buoyancy aids, lifejackets or aquatic toys.