When researching everything said that cardboard and a heat lamp is a no go...but everything I’ve learned today has kind of undone what is researched anyways. what’s the safest set up for cardboard and a heat lamp?
Make sure to have the lamp VERY well secured - do not rely on the clamp. Most lamps have a hanging loop on the back and that should be used. Some people even use the cord to help with that as well.
Also as I mentioned, a lower wattage bulb simply burns less hot, so slightly less risk if it shatters and lands on shavings or cardboard.