The Square D™ Extreme Duty QOU circuit breaker was developed specifically with the unique challenges of harsh environments in mind. The circuit breaker has specially constructed internal components that make it resistant to the damaging effects of high humidity and salt, which are common in commercial HVAC and wastewater treatment applications. The circuit breaker has passed a 500 hr salt spray test. The QOU circuit breaker is also appropriate for any application that endures a corrosive atmosphere or highly humid conditions, such as wastewater treatment. It is available in 30 or 60 A and can be used with standard QOU devices and accessories.