Role:** Senior technical writer specializing in international standards document

| Hydrocarbon | Standard AIT (ASTM E659) (°C) | Typical HSIT (Open Air) (°C) | Key Risk Factor | |—|—|—|—| | Methane | 580 | > 600 | High stability requires very high temp | | Propane | 470 | ~ 450? | Close to AIT | | n-Hexane | 225 | ~ 300? Wait. | | Gasoline (Representative) | 250-450 | 400-450? Actually, the standard warns about surfaces *lower* than AIT. | | Vapor/Setting | Min Ignition Temp (Surface) | |—|—| | Propane on flat plate | 520°C | | Propane in tube | 450°C | | Gasoline on flat plate | 480°C | | n-Hexane on flat plate | 350°C | | Hydrocarbon Vapor | Standard Lab AIT (°C) | Hot Surface Ignition Temp (°C) | Key Influencing Factor | |—|—|—|—| | Methane | 580 | 595 | Requires sustained high temp | | Propane | 450 | 470 | Surface area contact time | | n-Butane | 405 | 420 | Flow velocity effect | | n-Hexane | 225 | 335 | Lower than AIT? No, the standard might say open atmosphere ignition can be *higher* or *lower*. Specifically, for some hydrocarbons, ignition on a hot surface in open air can be harder than in a closed vessel? | Vapor | Closed Vessel AIT (°C) | Open Air HSIT (°C) | Cool Flame Temp (°C) | |—|—|—|—| | Propane | 490 | 520 | 340 | | n-Butane | 430 | 470 | 310 | | n-Hexane | 240 | 350 | 280 | | Gasoline | 250–450 | 480 | 260 | | Hydrocarbon | Lab AIT (°C) | Open Air HSIT (°C) | Cool Flame Risk (°C) | |—|—|—|—| | Methane | 580 | 595 | None detected | | Propane | 490 | 520 | 340 | | n-Butane | 430 | 470 | 310 | | n-Pentane | 285 | 400 | 280 | | n-Hexane | 240 | 350 | 260 | | Gasoline (Typical) | 250–450 | 480 | 290 |