Too close to a computer monitor?

Don't worry about this ... no known danger.

I wouldn't worry about that, the radiation from a correctly functioning monitor or TV should be within safe levels.

However I would worry about blocking vents, which could cause overheating and premature failure, or the animal drooling or pissing into the monitor, which could be fatal to the monitor and potentially dangerous to the animal . I had a rather expensive TV for repair a few years back where a tomcat decided to relieve himself into the top vents. The cat was OK but the TV was a mess. Horrible, sticky, pungent and worst of all highly corrosive and rather conductive gunk all over the electronics, and a few blown components.

Dave

I would also worry about cat or dog (assuming a normal range of movable pets) hair getting thru the small vents and into the set, and eventually causing some sort of failure. It would probably take a long time, but I would worry about that before I would worry about any EMC effects.

H. R. (Bob) Hofmann

Years ago when TV sets had tubes, some of the tubes in the high voltage section would emitt x-rays. Even then the x-rays were usually beaming down so you had to be under them to get very much radiation.

I would worry more about my monitor over heating because the vents were blocked.

My cat used to park herself on top of my PC monitor as irt was nice and warm (I'm not using an LCD display yet!) I was worried about ventilation and cat hairs getting into the unit so, reluctantly, I put a stop to it. Cheers, Roger PS. Meow, meow... the mean old sod, it was nice up there! Snuffles.

Sorry, but the main source of x-rays was the picture tube itself. Any device which employs 15000 or more volts, with electrons hitting metal with that energy will produce x-rays. Thats why lead bases front glass is used. Even so I would keep small children not to close to a color TV.

Ionizing radiation in CRT monitors is generated within the CRT itself, and most of it issues through the faceplate; that's why they're made of heavily leaded glass, and are very thick.

There's very little risk, and anyway, animals (presumably a cat) have such short lifetimes that any kind of radiation-induced damage just won't have time to develop the way it *possibly* could in a human.

Far more likely, the animal will block airflow through the monitor (they're never well cooled at best), and will limit *it's* lifetime.

Isaac

The HV rectifier tubes were known to produce small amounts of xrays, unlike the CRT, they weren't made of leaded glass. They were generally well enclosed in metal shields though.

"John Doe" bravely wrote to "All" (05 Jan 06 21:13:23) --- on the heady topic of "Too close to a computer monitor?"

JD> Subject: Too close to a computer monitor? JD> Xref: core-easynews sci.electronics.repair:354113

JD> I'm wondering about radiation levels at close range to the JD> electronics of a computer monitor.

JD> Specifically, I'm thinking about an animal lying on top of the JD> monitor vents when it's cold in the room (when monitor cooling is JD> not an issue).

JD> Is there a significant difference in potentially destructive JD> radiation at that close range?

JD> I vaguely recall hearing about some significant radiation at very JD> close range to specific components?

There is not enough voltage in a tv to produce significant X-rays. Perhaps the strongest source of EM radiation is when the unit is first turned on and the degauss circuit activates. Many times you may notice that a lamp on the same circuit will flicker. When the unit is running there is always a powerful radiation sweeping the area around it. Try for example wearing some sensitive headphones and bringing your head near the side of the unit and you will hear this field.

A*s*i*m*o*v

... Dunno if we'll get that past the CSA und UL 'owever.

The unions in some of the European countries (Seden primarily) made abig stink about this more than 10 years ago, asnd as a result standards were written that limited the external magnetic fields. There are two main sources of external fields, the x-rays from the high-voltage accelerated electrons hitting the acquadag on the inside of the tube and the shadow mask/screen on the front of the set, and the magnetic fields caused by the deflection yoke. Newer sets have figured out how to limit the external fields so you cat or dog or hamster or ferret or whatever probably should not have ite life shortened by the deflection fields. The x-rays in any solid-state set are produced entirely within the CRT itself. If you want to check for x-rays, you could contact someone at your local hospital to see if they have a gizmo they use around their x-ray machines to measure leakage, or you could expose a role of film in a plastic container to possible x-rays by placing it whre the animal sleeps for a couple of hours and then having it developed. If the film doesn't come back all clear, indicating no exposure to x-rays, then you can start ot worry. I still think the hair problem is the one to worry about.

H. R.(Bob) Hofmann

They used to use diode valves (tubes) as rectifiers for the EHT, and these could emit x-rays, when they were in the off-state, i.e. electrons hitting the filament when reverse biased. I believe (but have never seem for myself) that they also used beam triodes as shunt regulators to pull the EHT down to a stable level. The envelopes of these valves were not very thick. There are web pages explaining how to take x-ray pictures using these valves, but I believe that they overdrive the valves beyond their ratings in order to shorten the exposure times. The web pages mention that you want to find an earlier version of the valves made before they started worrying about x-rays and adding lead to the glass.

Chris