The governing standard for particle board is BS EN 312:2003. It classifies the various panel types according their strength properties and moisture resistance.

Particle Board according EN 312:2003

General purpose, non-structural General load bearing applications
Heavy duty load bearing
P 1 General purpose - dry conditions P 4 Load bearing - dry conditions P 6 Heavy Duty Load bearing - dry conditions
P 2 Interior Fitments - dry conditions    
P 3 Interior Fitments - humid conditions P 5 Load bearing - humid conditions P 7 Heavy Duty Load bearing - humid conditions
Furniture, interior fitments and flooring are the major applications of particle board. Smaller size flooring panels are usually tongue-and-grooved. Particle board with melamin overlay is common. The timber trade is running a merchantable assortment of raw, tongue-and-grooved, melamine ovderlaid and veneered panels.