# Temperature of Neon Light

I recently installed a neon light in a configuration such that it is resting on a book shelf and near some books. I would like to know if this stupid/if it is going to start a fire if I leave it on without watching it. I'm also curious about how to calculate the temperature of the bulb by physical principles.

To be clear, I'm not going to leave the bulb on when I am not present and/or not awake until I've measured the equilibrium temperature and it is sufficiently low.

Parameters: the bulb is a 5 feet long. The outer radius is approximately 1.5cm. I don't know how thick the glass is. The bulb contains argon and mercury and emits a pink color. It presumably is made of glass and has a coating. By touch, the cathode/anode (? -- I think this is the terminology) is the hottest part. These nodes are enclosed in a plastic insulator. I can touch the lamp and the ends without burning myself after a few hours of it being on, which I am taking (correctly?) to be the equilibrium temperature. The lamp is at STP, defined as: in a room at atmospheric pressure and temperature, out of direct sunlight, and with ambient temperature unlikely to exceed 110 degrees F/45 degrees C at any time. (yes, I am American).

I can make more measurements or determine them with some amount of money/materials/effort if I have a sense of what the important measurements are.

So: the questions are:

(1) Practical: Should I worry about starting a fire

(2) Theoretical: How do I calculate the equilibrium temperature of the bulb given the voltage, current, number density of the gas, ratio of the two species, absorptive properties of the coating, length and inner+outer radius of the cylindrical glass bulb, and pressure and temperature of the surroundings. Or any other parameters I might not be thinking of.

(3) Characteristic: What are the characteristic values of these parameters that I should use.

Progress so far: the Internet tells me that Neon lights are a plasma with electron temperature between $10^5$K and $10^6$K, and plasma density between $10^{12}$ and $10^{20}$ in units of $cm^{-3}$. I don't know what this means. I would appreciate a reference.