Most germicidal bulbs look like linear fluorescent light bulbs. They have the same shape. They share similar base types. Both use low pressure mercury arc technology. They both have hot cathode and cold cathode lamp types. And both produce the same ultraviolet radiation inside the bulb.
So what’s the difference?
The fluorescent bulb is coated on the inside with a phosphor which converts ultraviolet to visible light. The germicidal bulb is clear and it is made of special glass which transmits the ultraviolet, primarily 253.7 nanometer wavelength radiation generated by the arc.
There are several types of glass used in germicidal bulbs depending on what wavelengths are required. For example, one type of glass bulb will block ozone producing radiation and another will allow it.
Because the glass of germicidal bulbs is clear and designed to allow powerful ultraviolet radiation to pass through it, users of these bulbs must be much more careful to avoid looking directly at them compared to fluorescent bulbs which block most of the UV.
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