2.5 & 4.0 IPM Horizontal The 2.5 & 4.0 Inch Per Minute Horizontal tests evaluate resistance of flame spread and the burn rate of materials when exposed to an open flame to show compliance with the requirements of 14 CFR §§ 23.853, 25.853, 27.853, 29.853, 23.855, 25.855, 27.855, & 29.855.Components that require 2.5/4.0 IPM Horizontal testing: Clear plastics windows/signsParts made from elastomeric materialsSeat BeltsShoulder HarnessesCargo/Baggage Tiedowns Please contact one of our flammability specialists to request testing or if you have any questions. 12 & 60 Sec. Vertical 45° Cargo / Baggage Panel 60° Wire / Cable Insulation Request Testing Request Information