RWA vs. NRWG: What is the difference?

In tenders and product data sheets, the terms smoke and heat exhaust ventilation (SHEV) and natural smoke and heat exhaust ventilation (NSHEV) often appear in the same sentence – and are frequently used synonymously. Technically, however, they refer to two different levels: the entire system and its certified individual component.

RWA: the system as a whole

RWA stands for smoke and heat exhaust ventilation system and refers to the entire system: triggering devices, control unit, electric window drives, and the openings themselves. We explain in detail how an RWA system is constructed and functions in our article. What is a smoke and heat exhaust ventilation system (SHEVS)?.

NRWG: the tested individual component

NRWG stands for Natural Smoke and Heat Exhaust Ventilation Device. This refers to a single building component – for example, a window, skylight, or facade vent – that has been tested and classified for natural smoke extraction according to EN 12101-2. An NRWG uses thermal buoyancy and wind to transport smoke to the outside without fans and is opened by an electric drive.

The difference at a glance

• RWA – the system level: interplay of triggering, control, drives and one or more opening elements
• NRWG – the component level: a single opening element tested according to EN 12101-2 with a defined aerodynamically effective area

To put it figuratively: A smoke and heat exhaust ventilation system consists of several smoke and heat exhaust ventilation units (SHEVs) that work together with the central unit and drives – just as a vehicle consists of several tested individual parts, but only drives as a whole.

Why this distinction is important in planning

Test certificates and classifications according to EN 12101-2 always refer to the individual smoke and heat exhaust ventilation (SHEV) unit, not automatically to the entire system. Anyone ordering SHEV-certified windows or skylights must also check whether the drive type, control system, and trigger mechanism are compatible as a complete SHEV system. You can read about which drive type is suitable for which component in our article. Chain drive, linear drive or rack and pinion drive?.

Conclusion

Smoke and heat exhaust ventilation (SHEV) and natural smoke and heat exhaust ventilation (NSHEV) systems belong together, but refer to different levels: SHEV is the overall system, NSHEV is the certified component that opens the smoke extraction area. Clearly distinguishing between these two terms avoids misunderstandings in tendering and planning – and ensures you know exactly what to ask for.