No film set in New York is complete without beautifully framed shots of steam rising in the streets. Since 1882, buildings can have steam delivered for the purposes of heating, cooling, cooking and sterilising. It obviates the need for a floor of vast boilers and the business of maintaining them. Steam, being lighter than air, can race vertically through a building’s radiators for rapid heating. One downside: the effect of ‘steam hammering’ where condensed water (formed when system is off) in a pipe is suddenly hurled forwards making a loud clanking sound. The last mega steam main explosion in 2018 closed 5th Avenue for weeks.