In Metro 2033, the first Tihar is available as early as the " Lost Tunnel" level. The sound of the gas leak will not alert the enemy of Artyom's position. In Metro: Last Light, it can be modified to stop the air from leaking.
It's possible to overpressurise the cylinder for extra stopping power or range, but the extra air will leak out eventually and the gun will revert to normal power levels.
A pressure gauge mounted on the right side of the weapon shows how much relative stopping power and distance the next shot will have, with each shot draining a small amount of air from the reservoir. The ammunition is propelled by a cylinder of compressed air placed inside the stock of the gun, which attains its pressure by a handpump at the end of the handguard. It carries fifteen 15 mm ball bearings in a tubular spring-fed magazine. The Tihar is extremely quiet and is capable of silently bringing down enemies from surprisingly long ranges. With pre-war laws, limitations, or regulations no longer applicable and with parts readily available, weapons such as the Tihar are a popular alternative to actual firearms. Despite some shortcomings in comparison with conventional firearms in use, the air guns seem popular in the Metro.