use a venturi effect to incorporate air into the water stream for a lighter massage effect; this requires another set of hoses. Some models use an air blower to force air through a separate set of jets for a different "bubbly" massage effect; this is a separate system from the induced air. An ozone system: ozonation is a common adjunct to water maintenance, and if installed will have its own set of hoses and fittings. Heating and energy use Hot tubs are usually heated using an electric or natural gas heater, though there are also submersible wood fire hot tub heaters, as well as solar hot water systems. Hot tubs are also found at natural hot springs; in this case, the water may be dangerously hot and must be combined with cool water for a safe soaking temperature. Effective insulation greatly improves the energy efficiency of a hot tub. There are several different styles of hot tub insulation: some manufacturers fill the entire cabinet with foam, while others insulate the underside of the shell, the inside of the cabinet, or both. Many manufacturers advertise the superiority of their approach to insulation, but few independent side-by-side comparisons are available. The hot tub pump and hot tub heater represent most of the power consumption in a hot tub and vary in use of power depending on their size. Energy efficiency of portable hot tubs has been studied by the Pacific Gas and Electric Company (PGEC), leading to industry responses and interest from both the California Energy Commission and Natural Resources Canada. California's portable electric hot tub listing include R values of thermal insulation, and standby watts. In 2019 an update to the ANSI standard for energy efficiency was approved. For the first time, this new standard increases the minimum energy efficiency level for portable spas and inflatable spas. Hot tub covers have been shown to reduce most of the evaporative losses from the pool when not in use. With this component of heat loss being 70%, a cover with even a small R-value is able to achieve as much as a 75% reduction in heating costs when used as opposed to leaving the water surface exposed. There are several different types of spa covers. Some covers are better for insulation and therefore are lighter on internal parts and energy efficiency. Some examples of covers are insulated, aluminum, rolling, or a tonneau. Sanitation