When heated air is released into an enclosed space it has a natural tendency to stratify, creating a temperature gradient from floor to ceiling. In many cases the floor temperature might be 15°C, whereas the roof temperature can reach 25°C, or higher. Generally, the hotter the roof fabric; the greater the heat loss from the building. Energy loss through the fabric of the building in this way can substantially increase operating costs of the heating system.

Over the years a number of methods have been developed aimed at decreasing the temperature gradient from floor to ceiling, and within the H&V industry this is known as "de-stratification". All heating systems result in a degree of stratified air, some far greater than others.

Typically, storage warehouses and manufacturing facilities are heated utilising 'floor-standing', or 'suspended' gas-fired warm air heaters, or overhead 'radiant' systems. In older premises, suspended 'unit heaters' served by a central boiler can often be found.
In every case, stratified air will result, despite what the individual heater manufacturers might claim.

As with most particular sectors of an industry there is usually one product superior to all others for a particular purpose. In the H&V industry, with regard to "de-stratification", the product best able to achieve consistent and high fuel-input savings is "DESTRATAIR" provided by PRICE TWA.