Phase-out of incandescent light bulbs were no longer available from European sources. Russia is phasing out incandescent light bulbs. The production of lamps of 100 watt and more is banned. There are also discussions to ban light bulbs of 50 watts and more. Switzerland banned the sale of all light bulbs of the Energy Efficiency Class F and G, which affects a few types of incandescent light bulbs. Most normal light bulbs are of Energy Efficiency Class E, and the Swiss regulation has exceptions for various kinds of special-purpose and decorative bulbs. In line with EU rules, Switzerland banned the import and manufacture of halogen
Incandescent light bulb the bulb inner surface and reacts with hydrogen, decomposing to metallic tungsten and water. Water then cycles back to the filament. This greatly accelerates the bulb blackening, in comparison with evaporation-only. The gas layer close to the filament (called the Langmuir layer) is stagnant, with heat transfer occurring only by conduction. Only at some distance does convection occur to carry heat to the bulb's envelope. The orientation of the filament influences efficiency. Gas flow parallel to the filament, e.g., a vertically oriented bulb with vertical (or axial) filament, reduces convective losses. The efficiency of the lamp increases with a larger