lampuista vielä

kaasun olevan argonia (Ar). Sehän on jalokaasuista yleisinkin; likimain 1 % ilmasta on sitä.

Koetinpa googlatakin. "light bulb fill gas" tjsp.

"At first, incandescent bulbs were made with a vacuum inside them. Air oxidizes the filament at high temperatures. Later, it was discovered that filling the bulb with an inert gas such as argon or an argon-nitrogen mixture slows down evaporation of the filament."

...

"Sometimes, premium fill gases such as krypton or xenon are used. These gases have larger atoms that are better at bouncing evaporated tungsten atoms back to the filament. These gases also conduct heat less than argon. Of these two gases, xenon is better, but more expensive. Either of these gases will significantly improve the life of the bulb, or result in some improvement in efficiency, or both. Often, the cost of these gases makes it uneconomical to use them."

http://members.misty.com/don/bulb1.html

Siis: argon, argon/typpi-seos, krypton tai ksenon.