<?xml version="1.0" encoding="utf-8"?><mads xmlns="http://www.loc.gov/mads/" xmlns:mods="http://www.loc.gov/mods/v3" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.loc.gov/mads/
mads.xsd"><authority><topic authority="http://AATesaurus.cultura.gencat.cat/aat/getty_en">vacuum heating</topic></authority><related type="broader"><topic>steam heating</topic></related><variant type="other"><topic>vacuum return systems</topic></variant><variant type="other"><topic>heating systems, vacuum</topic></variant><variant type="other"><topic>heating, vacuum</topic></variant><variant type="other"><topic>return systems, vacuum</topic></variant><variant type="other"><topic>systems, vacuum heating</topic></variant><variant type="other"><topic>systems, vacuum return</topic></variant><variant type="other"><topic>vacuum heating systems</topic></variant> <note xml:lang="en"><![CDATA[ Steam heating systems that include vacuum pumps that separate air from condensation in the return main of the system, maintaining the pressure at a constant level and accelerating the circulation of steam. ]]></note></mads>