@R05339@ that contains mercury vapour at pressures of about \(0.1\ \text{Pa}\) (\(0.75\times 10^{-3}\ \text{Torr}\); \(1\ \text{Torr} = 133.33\ \text{Pa}\)). At \(25\ ^{\,\unicode{x26ac}}\text{C}\), such a @L03447@ emits mainly at \(253.7\) and \(184.9\ \text{nm}\). They are also called germicidal lamps. There are cold- and hot-@C00905@ as well as cooled electrode-less (excited by microwaves) low-pressure mercury lamps. The @W06682@ is a low-pressure mercury arc with an added fluorescent layer that emits in the UV-A spectral region (\(315\)-\(400\ \text{nm}\)).