Safety
Safety
This domain tests hazard recognition and control: confined spaces, gases, chemicals, electrical equipment, traffic, slips, pathogens, and cold-weather hazards. North Dakota operators work around wet wells, digesters, chlorine and sulfur dioxide, and icy walkways, so the exam favors practical decision questions.
Core rules
- Permit-required confined spaces need a permit, atmospheric testing, ventilation, an attendant, and rescue provisions.
- Test atmospheres before entry and continuously: oxygen, flammables, then toxics.
- Acceptable entry oxygen is about 19.5–23.5%; flammable gas alarm is commonly 10% LEL.
- Lockout/tagout controls unexpected energy; never bypass a safety alarm.
- Chemical hazards require SDS review, PPE, and eyewash/shower access.
Worked example
A gas meter reads 18.9% oxygen, 3% LEL, and 8 ppm hydrogen sulfide at a wet well. Oxygen is below the 19.5% entry threshold, so do not enter. Ventilate, retest, and keep the attendant outside. After ventilation, readings of 20.5% oxygen, 0% LEL, and 2 ppm H2S are within common entry ranges, but entry still requires a permit and continuous monitoring. The reasoning: the first failing reading stops entry; a later acceptable reading does not remove the permit requirement.
Traps
Testing only at the top of a space; assuming odor detects H2S (olfactory fatigue is real); entering to rescue without PPE or backup; treating oxygen-enriched air as safe; ignoring traffic control at a street repair.