US Patent 7839281 Explosion indicator for explosion-proof enclosures

Indicator devices and systems for explosion proof enclosures are described. The indicator devices include a sleeve, a dome-like transparent member, a connector body, a first and second contact, a means for preventing the first contact from contacting the second contact, and an indicator. Upon an increase in a temperature or a pressure near the means for preventing (for example, within the enclosure), the means for preventing allows the first and second contacts to contact, thereby completing an electrical circuit from a power source to the indicator (such as a light or an alarm). The indicator systems include an indicator device coupled to an explosion proof enclosure containing critical equipment.