It is difficult to drive theoretical concepts into the minds of students who like to work with their hands.

What I ask all students to know when they complete my courses is a list of eight critical truths related to HVACR. This list is asked for both on the midterm and final exams. This is an imperfect list; however, it endeavors to lock in critical knowledge that the HVAC professional must always consider in his or her work.

HVAC professionals must always know the following:

1. HVAC equipment is Heavy, check load bearing ability of structures and floors.

2. Poor combustion results in undetectable CO, which can kill people.

3. Fuel can Explode at certain fuel to air ratios, which can kill people.

4. Things eXpand when heated and contract when cooled, which can tear apart systems.

5. High surge Pressure is produced by the closure of fast acting valves, which can tear apart systems.

6. Smoke travels through ducts, which can kill people.

7. Water expands as it freezes, which can tear apart systems.

8. Refrigerants can suffocate people.

I have developed the following mnemonic that is helpful in memorizing these key concepts: "Heating and Cooling EXPerts Set World Right." Many professionals would add many more items to this list but I believe these eight facts encompass important safety and catastrophic destruction concerns in mechanical systems.