Wellis Air OH cartridges last 3 months each for nonstop surface and air cleaning your space. 2 Cartridges are already included with your purchase of a Wellis Air unit. The sun's ultraviolet rays are combined with moisture in the air to create atmospheric hydroxyls that clean and protect the earth's environment. Wellis Air's patented technology replicates Mother Nature to provide a constant stream of hydroxyls that destroy contaminants on both surfaces and in the air. No virus can survive without hydrogen. Wellis Air steals the hydrogen from viruses and combines it with OH radicals to form H2O. That's right. We take viruses and turn the output into water molecules.

Limonene Scent Safety Sheet here