absorbs harmful radiation and emits therapeutic radiation the second filtration layer 404 is substantially transparent to the therapeutic radiation but substantially opaque to harmful radiation fig4 illustrates schematically a situation where a considerable amount of incident harmful radiation 406 and a relatively small amount of incident therapeutic radiation 408 are incident upon the first layer 402 the first fluorescent layer 402 absorbs a certain amount of harmful radiation and both transmits and emits therapeutic radiation so that a reduced amount of harmful radiation 416 and an enhanced amount of therapeutic radiation 418 reach the second filtration layer 404 the second filtration layer 404 filters out the remaining harmful radiation so that substantially no harmful radiation passes through the material 400 but so that substantially all of the enhanced amount of therapeutic radiation 418 exits the material it will be appreciated that fig4 is an exploded view and that in practical embodiments the layers 402 404 would usually be in contact with each other it should also be appreciated that the representation of the radiation is schematic and that the incident harmful and therapeutic radiation would be likely to be components of the spectrum of sunlight in one embodiment the second filtration layer 404 can be a coating applied to a first fluorescent layer 402 which is in the form of a fabric the coating could comprise nano particles of inorganic substance such as a suitable metal oxide such as zinc oxide which have been found to be effective in filtering ultra violet radiation while allowing transmission of visible light it is to be understood that if any prior art publication is referred to herein such reference does not constitute an admission that the publication forms a part.