In hydrogen piping, threaded and flanged connections are restricted to what areas?

The correct answer highlights that threaded and flanged connections in hydrogen piping are primarily restricted to hydrogen cutoff rooms and outdoors due to safety considerations. Hydrogen poses unique risks because it is highly flammable and can lead to leaks if not properly managed.

Hydrogen cutoff rooms are specifically designed areas where potential leaks can be contained and managed effectively. By only allowing these types of connections in locations that have enhanced safety measures, the risk of a hazardous situation occurring is minimized. These rooms typically have ventilation and other safety systems in place to address any potential hydrogen accumulation.

Furthermore, allowing such connections outdoors takes advantage of natural dispersion in the event of a leak, significantly reducing the risk of explosive atmospheres that could result if a leak occurs indoors where ventilation could be limited.

In contrast, using these types of connections in buildings or high-rise structures presents additional challenges and risks, especially where confined spaces and the presence of ignition sources may increase the potential for accidents. Thus, the restriction to designated areas is a critical safety standard.