Tobacco leaves are highly moist up until they are harvested, then depending on their type and the final use, the ERH can vary quite significantly, so measurement and control is a significant factor in processing environments and the product quality.
Tabacuba & Xuchang Tobacco Factory
ERH is a key factor in quality (Cigars especially), hence the use of humidors in the storage of the best quality products. Handrolling tobacco is usually has a high ERH value, taylor mades - medium ERH. Handheld insertion type instruments are used in bulk checks, water activity units tend to be used in the laboratory environment.