Arrived on site to perform diagnostic on system. Homeowner states that the system is working and is heating the home, but a couple days ago there was a critical alert that had popped up. It has since gone away and hasn’t happened again, but would still like everything checked. Checked history on thermostat for any alerts and there are none present. Also tried to recall any codes from indoor circuit board but there were none present. Cycled system for heat. Verified proper heating sequence of operations and system is heating normally. Checked all electrical and heating components, everything is in order. System is operating as it should. Homeowner also mentioned that she noticed a hole in the return plenum that looked odd, but after inspection found that hole that she was referring to was just a temperature/pressure port. Hole is necessary to take pressures and temperatures, and should always be sealed off with tape as it is now. Lastly, homeowner was upset that she realized that smar