Critical listening demands volumes that do not tire the ears, thus temporarily (potentially permanently, as well BTW) damaging your most important tool.
Keep it under 90 dB max with your target average being 80 dB - 85 dB and you should be OK.
Of course if you are already deaf from not using this information to guide your past listening habits you may need 130 dB to even get an idea that there is some recorded material being played back on your monitors.