It turns out they are somehow right.Plasmas create light with tiny pixel-sized buckets lined with a material known as luminescent phosphor. These wells are filled with a rare gas (such as argon). Electrodes cause the gas into a plasma, which releases UV light, which makes the phosphorus glow a specific color: red, green or blue. The gas pressure and the strength of the panel structure / glass are evaluated with respect to the external air pressure at sea level ....
As you head into space, the air is thinner and there is less pressure. Since plasmas are sealed, the noble gas expands, pushing the glass to share a little bit. As such, it makes it a little harder for electrodes mounted on the front of the glass to make their electronic magic. As they work hard, they drink and do a little extra noise. It's not much, but in a quiet room without TV audio, you could probably hear. It will be stronger with larger screens, or during very bright scenes (think white material essentially like hockey or skiing, and / or brighter picture mode as Vivid or Dynamic). Plasmas have gotten a lot better designs have become more robust, and the glass used has become stronger, so it is much less of a problem than in the past.
How much less of a problem? I asked LG, Samsung, Panasonic and what their altitudes were evaluated for TVs. Here's what they told me: LG: 2900 meters / approx. 9500 feet
Samsung: 2.100 m / 6.900 ft ~
Panasonic: 2.200 m / 7.200 ft ~ (VT, GT, ST, UT, U series), 2600 m / 8500 ft (XT and X series)
(Note: this data is Panasonic 2012, 2013 data were not available LG and Samsung is the same for both.).
So what does that mean? Well, Denver is about 5400 feet, it is very good. Santa Fe 7200, just about Panasonic and Samsung, but LG. People in places like Breckenridge (9,600 m), La Paz (11,942 ft), or the Ronconada, Peru (16,728 ft), maybe consider LCDs. If you plan to hike Everest, let your plasma at home.
Bottom line
You must be high enough to not want a plasma. Or is it, high enough to not be able to get a plasma. Probably the latter. If you're ready for a rarefied altitude and are concerned can hum, consult a local store (if possible). If there is a buzzing, you'll be able to hear there, or when you connect your new TV home.
If you live at a high altitude, should you should consider an LCD screen on a plasma because of it? Maybe. On the one hand, it seems logical to an outsider point of view that if you're driving electrodes harder (or even different), it may have accelerated wear, especially in the provision of any importance TV power. On the other hand, no plasma manufacturers call this number, as they are the ones who have the most to lose if there was life, performance, or other problems at high altitude, one might think that 'they would. Even if it's just to cover their butts ....
