Disassembled General Electric RCD. 
<ul><li>Reason of damaging: when I checked panel devices in the distribution board, I've found, that pushing "test" button on this RCD is causing sparks instead of triping. As the device is not working, it should be replaced. OK, I removed the cover to take RCD from DIN rail. What I have seen? This 25-Amps RCD was protected by 50-Amps circuit breaker.
<ul><li>What's wrong?</li>
<li>-The structure of this device is designed for normal work up to 25A. If you increase the maximum allowed current, it will heat more than allowed limits. Overheating can spoil some parts and main details wouldn't supply proper work to device.</li></ul></li></ul>
I wouldn't frighten you about fire or deaths caused by improper using of electric devices. But it could melt due to overheating and damage other devices inside distribution board (imagine the expenses replacing whole distribution board); and someone could get quite strong electric shock touching metal cover which is protected by faulty RCD.
<a href="//commons.wikimedia.org/wiki/User:Dmitry_G" title="User:Dmitry G">Dmitry G</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>