Well, it’s true. The stationary engineer / boiler operator is a dying trade. There is not enough young people interested in this type of work.
One way to make sure you keep the employees you have is by giving them some incentive. For example, let them know they are thought of and you care about their well being. If an employee doesn’t show up for work and there is no reason why (even though his time off was already approved), why not call the local police department to check on them and break into their house.
When the employee gets home and finds police officers all over his property, they can then have a discussion about the golf outing and what he scored.
You can’t make this stuff up.