CROSS

A pneumatic cross typically refers to a four-way pneumatic fitting used to connect four air lines at a single point, allowing the air to branch out or converge. It is a type of manifold fitting in compressed air systems that provides a single intersection with four ports arranged in a cross shape (like a '+'), facilitating the distribution or collection of air flow. In a different context, a cross-connection in plumbing or fluid systems (which can involve air/gas/pneumatics) is an actual or potential connection between the potable (drinking) water supply and a source of non-potable or contaminated fluid (liquid, solid, or gas) that could cause backflow and pollute the drinking water. In this case, "pneumatic cross" might imply a dangerous connection allowing non-potable air or gas into a clean water line, requiring a backflow prevention device.