Reddit mentions of Meterk EMF Meter Electromagnetic Field Radiation Detector Handheld Mini Digital LCD EMF Detector Dosimeter Tester Counter

I'm not a targeted individual, and frankly I don't think you are either, but I'll proceed in giving you the benefit of the doubt anyway.

First, you need undeniable physical evidence. Get a Geiger counter (you can find a relatively cheap and well-reviewed one on Amazon here) and read up on the measurements that a Geiger counter will give you with this chart. If the radiation is causing you significant physical harm like you've described then it is likely ionizing radiation, which a Geiger counter can accurately measure.

Your references towards being affected by electrical appliances sound more like elecromagnetic radiation though, which is quite different from ionizing radiation. A device like this can be used to measure ambient EMF radiation. Again, make video documentation to prove that you're being exposed to extremely high levels of it.

If you're concerned about the possibility of your video evidence being tampered with, as many TIs seem to be, you can upload that video evidence to a storage medium such as FreeNet (/r/freenet), which will split the video file into many, many pieces and distribute them to thousands of volunteers worldwide so that the original file can be retrieved later. The data in the pieces that are distributed to the volunteers is encrypted so they won't know what they're holding on to for you, so even if they were complicit in the alleged gang stalking they wouldn't know that you (as the uploader) were someone they needed to fuck with. (This is, of course, a very brief explanation of the inner workings of FreeNet which leaves a lot out, but you get the gist of it.)

Now for the suggestion you're not going to like. See a mental health specialist. If you're correct, and you have the evidence to back it up, you can get yourself a clean bill of mental health that you can present at future court proceedings to help validate the fact that there is a grand conspiracy against you. And if you're not correct, and you are mentally ill, you can get help.

You should travel a considerable distance from where you live to contact the mental health professional, because the conspiracy against you is certainly localized to some degree. However unlikely, it is possible to buy out local mental health professionals, but it is simply not feasible to buy out every mental health professional in the entire country on the off chance that they might have one particular person come in that they need to conspire against. You aren't a rambling nut job, so I am confident that you will agree that it's astronomically unlikely that a conspiracy against you would span more than a small network of a few towns. With this in mind, seeing a somewhat distant mental health professional seems like a logical option in a plan to fight this attack on you.

If you need any more guidance beyond what I've already typed up, just ask and I'll help you as much as I can.

A faraday cage will block electromagnetic fields (EMF). You can make one with simple chicken wire or similar. Any conductive material in a mesh configuration (or solid like aluminum foil).

The real question is why are you worried about it? Is it causing interference with equipment of some kind?

Keep in mind that you can measure the electromagnetic fields with a Gaussmeter. Unless you're standing directly underneath high-voltage power lines or are right up next to it, your exposure is about the same as as normal backround EMF levels in your house just from having power, sockets, devices, etc. in your house.

Some people are sensitive to high levels of EMF. It can give you vertigo, paranoia, etc. This EMF meter can give you an idea of your exposure. In a server room, I expect it to be pretty high anyway.

Others have already covered the other sources: CO, air pressure, white noise, etc.