On January, 1st 2018 I started the year with a huge scare.
I was rebuilding a R&S CRTU from different spare parts and one component was the RF Input module. The one I had was broken and I got a new one. I know what was broken, so after assembling the CRTU (which was working fine now), I opened said RF Input module, to see how difficult it was to access the broken component and to generically clean it, as some forum members said that cleaning the boards sometimes improved the component's performance.
Indeed, after opening the module, there was a lot of white pouder, some oxide. So i started cleaning it with different tools and at the end I was blowing on it.
After doing it, or better, while doing it, I noticed the sticker on the module saying "DANGER - BeO - Handle with care" (or something similar). Uhhh! I Googled BeO and guess what: it is a white powder, which is highly toxic, poisonous and cancergen. All in one.
Now I had two options: either it was just Aluminium oxide or it was in fact Berylium oxxide.
To make it short: I called the national hotline for poison issues and aftter they asked me some questions (what I was doing, how long was the exposure, what sympthoms, etc.), they said it was probably nothing.
Also, I found out that the white powder was certainly Al2O3 and not BeO.
The BeO is used in high power components like resistors and/or capacitors or transistors (not sure), so unless you dessolder them or break them anyhow, it should be OK.
Anyway, the stuff is highly toxic and that means you cannot just dispose of a CRTU or CMU200 in the household garbage bin.
Other test equipment may have even worse elements inside, like radioactive stuff.
Sure enough, if the device is not tampered, all is OK, but the warning labels are on it and these devices require special care and paper work.
BeO:
https://en.wikipedia.org/wiki/Beryllium_oxide#SafetyOhh, another very toxic element is Yttrium, which is often used in the YIG of spectrum analyzers!
https://en.wikipedia.org/wiki/Yttrium#PrecautionsRegards,
Vitor