Controls include enclosing the source, limiting source intensity, and shielding or filtering the source from the eyes. For example, portable panels screen welding operations so that the bright source does not reach people. Welders should wear protective eyewear with the applicable filter density for the type of operation (see Chapter 28). Carbon arc lamps are enclosed except for the aperture to direct the light where it is needed. Lasers with dangerous levels of visible light also have enclosures.