Fires like in the vehicle tunnel of St. Gotthard (Switzerland, 2001), Tauern (Arlberg Austria, 1999) and Mont Blanc (France, 1999) as well as in train and subway tunnels, i.e. Channel (1996) and in the Kings Cross underground station (1987, 2005) have exposed the devastation underground fires may cause. In each of these cases, the fire was far worse than any risk assessment had predicted and it has become apparent that still little is known about the behaviour of fire in confined underground situations. In many underground facilities and in vehicular tunnels it is necessary to have a forced ventilation system, to maintain comfortable levels of fresh air and to control the spread of smoke in the event of a fire. This can have a substantial effect on the severity of any fire that might occur. Predicting fire behaviour is an important part of tunnel design: different geometries and different ventilation systems will affect fire behaviour in different ways. Past and recent tunnel and subway disasters made it obvious that fire simulations are of essence when planning the response to such emergencies.
NILOX generators generate hot smoke, non-staining white smoke  ideal for simulating fires in tunnels and confined areas under controlled conditions.