Subtypes include one-hitters, bubblers, chillums, glass blunts, corn cob pipes, and standard hand pipes. Doyle also designed Portland's iconic public drinking fountains known as Benson Bubblers. In some regional dialects, water fountains are called "bubblers". These fountains, known as "Benson Bubblers", are still in use in downtown Portland. As of March 2014, these fountains, known as "Benson Bubblers", remain functional in downtown Portland. Oil bubblers are filled with mineral or silicone oil. Bubblers also have limited gas flow rates. Oil bubblers can tolerate an underpressure in the reaction vessel. It subsequently made the UK disco chart breakers/bubblers listing. Two bubblers exist outside of Downtown Portland. Mercury bubblers are largely similar in construction to oil bubblers. Conservationist Francis J. Murnane was instrumental in preserving the bubblers, his first successful project. Oil bubblers are predominantly used; the oil is inexpensive and not toxic. Gas bubblers are used to exclude air from a reaction or a system.