Effect of low-pressure and oxygen-enriched environment on combustion characteristics of typical fabrics

Artificial oxygen enrichment devices are used in several situations to ensure the safety and health of workers and travelers in high-altitude regions, such as in high-altitude airport control command centers, VIP rooms, medical rooms, and luxury hotels. Indoor oxygen enrichment can meet the oxygen supplementation needs of people. However, the flammability of materials is affected in nonstandard atmospheric conditions such as low-pressure and oxygen-rich environments, resulting could cause additional fire hazards.

This study simulates the combustion of typical indoor fabrics in the Kangding Plateau (60.5 kPa) and Guanghan, Sichuan (95.8 kPa) inside a combustion chamber by adjusting the pressure and oxygen concentration. It explores changes in the core combustion parameters such as flame form, ignition time, mass loss rate, heat release rate, and total heat release amount of pure cotton and polyester at 60.5 kPa and various oxygen concentrations (21.0%, 27.0%, 33.0%, and 39.0%).

Fabric combustion at low pressure involved the stages of thermal decomposition, ignition, intense burning, and flame decay until extinction. In a low-pressure environment with normal oxygen content, complete cotton combustion was achieved, resulting in the formation of residual char that was loose and easily pulverized. In contrast, polyester combustion exhibited an efficiency of only 11.1%, producing a considerable amount of black and brittle residual char. The rates of mass loss and heat release decreased during the combustion of cotton and polyester, resulting in lower flame heights. The ignition time of cotton decreased by 3.6%, while the ignition time of polyester decreased by 7.8%. The duration of combustion increased by 46.8% for cotton and 197.0% for polyester. Additionally, the burning time of melted polyester droplets increased by 296.0%. With an increase in the oxygen concentration, the ignition time of pure cotton and polyester decreased by 19.1% and 25.7%, respectively. The time of peak rates of mass loss and heat release for pure cotton and polyester were reduced by 78.1% and 52.1%, respectively. The flame height of both materials increased, and the peak mass loss rate and heat release rate significantly rised. The combustion efficiency of polyester was improved by 68.1%, and the total heat release was increased by 1.2 times. Additionally, the burning time of melted droplets was increased by 3.1 times. In contrast, the changes in these parameters were not considerable for cotton combustion. The decrease in the partial pressure of nitrogen in a low-pressure environment decreased the flame-retardant effect of the inert nitrogen gas. Thus, if the peak rate of heat release was taken as the criterion for a fire hazard, the combustion fire hazard of fabrics at a pressure of 60.5 kPa and oxygen concentration of 30.0% was equivalent to that of combustion under normal pressure and normal oxygen conditions.

This study analyzes the effects of the changes in oxygen concentration at low air pressure on the combustion characteristics and reveals the fire behavior characteristics of typical combustible materials such as cotton and polyester in low-pressure oxygen-rich environments. It provides a basis for the fire safety design of artificial oxygen enrichment environments in high-altitude regions.