I have a radiometer and periodically check my curing lights, but could you tell me what is the lowest acceptable intensity for LED and halogen curing lights?

Ideally, both quartz-tungsten halogen (QTH) and LED curing lights should have an output of at least 400 mW/cm² to ensure adequate curing. It is also important to make sure that the curing tips are kept clean of composite or other debris and that the filters in halogen units are replaced as needed.