You can blow them the wrong way round to "free them up"
best way is to get them really hot till they smoke all the crap off, a big heater blower or a paint gun or some people heat them up with a big bbq or gas burner
I`ve not done too much of that but I use a carbon filter on my vape`o`bong rig and I normally vape @200c or below I set my hot air blower up to max sometimes and fire it into the carbon to clear it out, means I get good airflow again without having to change the carbon
Sometimes I`m less lazy and just change the carbon
but for sure your can heat them up to clear them out, but if you`ve been using them in a grow they gas they give off will stink of herb