A gum disposal pocket includes a back wall, a pair of foldable side wings extended from two sides of the back wall respectively, a holding panel extended from a top side of the back wall and adapted for holding the pair of side wings in position, and a pocket cover extended from a top side of the front panel and adapted for closing and sealing the gum disposal pocket. A system including the optical device and a substrate, is also provided. The gas purification system also includes a second valve element having a second aperture to selectively connect a second port opening of a vessel to an input of the second valve element. The panels are placed end to end on their edge on the first floor of the building and joined to the building’s foundation and to at least one other horizontally adjoining panel.