Sprinklers in a rack shall discharge not less than how many psi for all classes of commodities?

The correct answer is 15 psi, as this is the minimum pressure required for sprinklers discharging on rack storage systems for all classes of commodities. This standard is established to ensure effective coverage and adequate water distribution for fire protection in facilities that store goods in racks.

When sprinklers operate at a pressure of 15 psi, it allows for a consistent and reliable performance, which is essential for suppressing fires in these storage configurations. If the pressure were lower, there might not be enough force to effectively distribute the water needed to control or extinguish a fire in an environment where combustibles are stored closely together, increasing the risk of rapid fire spread.

Higher pressures, such as 20 psi or 25 psi, are not the minimum requirements set by the codes for all commodity classes in rack storage, though they might be applicable under specific conditions or to meet different fire safety standards. Lower pressures, on the other hand, would not meet the necessary criteria for effective fire suppression, highlighting the importance of adhering to established guidelines for sprinkler systems.