A new design of moss bag to monitor metal deposition both indoors and outdoors

Moss bags have been widely used to measure aerial metal deposition rates out of doors. This paper describes a simple device whereby the relative humidity of mosses exposed indoors may be maintained at >95% permitting the extension of the moss bag technique to indoor environments. The comparability of irrigated moss bags with greased petri dishes or standard deposit gauges is demonstrated. The relative humidity of the moss is shown to be an important factor in controlling the efficiency of metal collection by moss bags.