Mercury (Hg) emitted to the atmosphere from various natural and anthropogenic sources can be transferred over long distances and accumulate in remote areas. Elemental mercury and all mercury compounds are highly toxic and pose negative effects on the environment and humans. Background air monitoring enables to assess and modeling the Hg environmental cycle, transport, and fate. We present data obtained throughout different years (2001–2023) in Japan, Europe, Russia, and South Africa using the Lumex mercury analyzers and monitors, as well as examples of identifying industrial sources of mercury emissions based on long-term air background monitoring. The observations of 2001–2006 in Minamata city (Kyushu Island, Japan) revealed seasonal variations of the background Hg concentration and also local anomalies attributed to industrial sources, such as power plants and a chemical factory. At the Listvyanka station located on the shore of Lake Baikal (Siberia, Russia), air monitoring has been running since 2011 within the GMOS/GOS4M networks; it was shown that mercury is transferred from remote emissions sources, such as coal combustion plants and smelters located 70 km away from the monitoring point. The analysis of the air mercury datasets of 2007–2023 from various monitoring points in Germany, Italy, Poland, Spain, and other European countries reveals chlor-alkali and coal-fired power plants, smelters, waste incinerators as main industrial sources of mercury emissions. In South Africa, the observation at two industrial sites running since 2021 shows that short-term anomalies are connected with air masses coming from areas where coal-fired power plants are located.