How altitude affects the performance of a Plasma TV?
Plasma TV uses rare gases like xenon, neon and argon which are enclosed between two glass sheets. For the optimum performance of the plasma TV, there must be a balance between the pressure of these gases inside the plasma display panel and the atmospheric pressure. In other words, both the pressures should be more or less equal for optimum performance. However, when the altitude increases, say above, 2500 ft above sea level, the atmosphere becomes thinner, resulting in low atmospheric pressure. In such conditions, the gases inside a plasma TV tend to work hard to produce the display. During this process, a plasma TV usually produces more heat and a sort of buzzing noise when it is working.

Most of the plasma TVs are designed to work at sea levels or within 3000 ft ASL. However, if you happen to live in higher altitudes, say in a place over 5000 ft ASL, you should go for a plasma TV which is especially designed for such conditions.

It is fairly easy to find out whether your plasma TV struggles to cope up with low atmosphere outside. One way is to feel the heat emitted by your TV. Another way is much easier the buzzing noise can be heard when your TV works much harder. Nowadays, this problem is being eliminated as newer plasma TVs come with design and calibration suitable for higher altitudes