This filter drier is a part of an air conditioning plant room. This type 4 Freon-based air conditioning system was built between 1964 and 1967 by L Sterne and Company Limited, an engineering company based in Glasgow. This air conditioning plant was installed at 7 Rolls Building, Fetter Lane, London.

The 19th century saw the development of mechanical refrigeration through the use of vapour-compression technology, pioneered by chemists and engineers such as Carl von Linde and Thomas Bell Lightfoot. These systems work by using a refrigerant gas and cyclically compressing and expanding them to extract heat from one room and passing it another, creating cold air.

Whilst early designs of mechanical refrigeration systems used ammonia or C02 as their refrigerant gases. Freon was developed during the 1920s as a non-toxic, synthetic replacement to other natural refrigerant gases. Freon is a trademark umbrella which encompasses several slightly different synthetic chemicals and can be broadly divided between chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs). As Freon gases became more efficiently synthesised and more cheaply produced, Freon became arguably the dominate refrigerant in the second half of the 20th century.

This particular type 4VP air-conditioning system uses R-22 Freon and was built by L. Sterne and Company Limited between 1964 and 1967 when it was installed at 7 Rolls Building on Fetter Lane in London. This was, at the time, the headquarters of Ernst & Young, one of the four largest international accounting firms.

In the 1980s the effects of Freon and other greenhouse gases were discovered, beginning a wave of increasingly strict regulations governing the production, distribution and use of Freon. CFC varieties of Freon have been widely banned, and HFC varieties of Freon are under heavy restriction.

The Freon used in this air-conditioning system, R-22 (a HFC), is now being phased across the globe as part of the 2020 Montreal Protocol, potentially ending in 2030.

Collections Review assessment drawing on tech files, and secondary sources.