Connect the installation timer to your master fader and the installation will fade out after #nMS since the last detected event.
mp.monoverb~
This is a little wrapper for monoverb~ by Olaf Matthes.
http://www.akustische-kunst.org/maxmsp/ This is a link to Olaf's page of great max msp externals. You will need to download monoverb~ from there and put it in your search path along with the other tinpark externals related to this wrapper. Use it in a bpatcher for best results as per the screenshot and helpfile.