When working inside a steel heating boiler, which of the following safety precautions should you take?
1. boiler must be cooled and vented
2. valves must be closed and locked, and all lines to and from the boiler must be blanked
3. you may use ungrounded wiring
4. always have one man standing outside, whenever anyone is inside the boiler
a) 1, 2, 3
b) 2, 3
c) 2, 3, 4
d) 1, 2, 3, 4
e) 1, 2, 4
Answer: E