When sourcing pepper spray, the most important metric is the Major Capsaicinoids (MC) percentage, which typically ranges from 0.5% to 2.0% for professional use; this determines the actual heat level rather than just the OC percentage. You must also verify the spray pattern (stream, fogger, or gel) to suit specific usage scenarios, and ensure the effective range meets a minimum of 3 to 5 meters for user safety. Additionally, check for leak-proof safety locks and a shelf life of at least 3 to 4 years to ensure reliability during emergencies.