For cabin and cargo compartment components inside aircrafts, one international standard that is typically used for determining material compatibility in terms of it being flame retardant is the FAR 25.853 (a). This test involves the use of a Bunsen burner, which can be run across the material or composite in the vertical direction, the horizontal or at an angle (eg. 45 or 60 degrees). The flame is in contact with the sample for a specified time frame and then the burn rate, burn length and time are measured. These parameters need to be within a specified amount to pass the corresponding requirement. For the horizontal burn test, the burn rate should not exceed 2.5 inches/min (~64 mm/min). The vertical test requirements are a bit more demanding compared to the horizontal test. However, the horizontal burn test is more than adequate and definitely relevant in many applications. For the vertical burn test, the material is subjected to 60 seconds of exposure in the vertical direction, the burn length should not exceed 6 inches (152 mm), the flame time should not exceed 15 seconds, and the drip flame time should not exceed 3 seconds. Based on the component within the aircraft, the appropriate flammability tests are performed to gauge feasibility. For example, for large cabinet walls, the vertical 60 second flame test is performed; while for acrylic windows the horizontal burn test is used.