It works by killing acne bacteria that infect skin pores. SIRs are porous particles, which contain an extractant inside their pores. Larger particles cannot enter into as many pores. A porous medium or a porous material is a material containing pores (voids). As the solution travels down the column some particles enter into the pores. Transpiration refers to the expiration of water through the minute pores or stomata of trees. This secretion layer may or may not have pores. This will remove supercritical pores from the body. Every membrane has pores in a range of sizes. The alveoli have interconnecting air passages in their walls known as the pores of Kohn. The ice accumulations grow larger as they attract liquid water from the surrounding pores. SEC works by trapping these smaller molecules in the pores of a particle. The water, seeping into pores and microcracks, has frozen there. Generally the larger the pores, the larger the spores. Permeability is an expression of the connectedness of the pores.