Sheet 28Mix-up sheet · Excavation, trenching and confined spaces
Confined space entry: who signs, who stays out, what you test first
Test oxygen first, flammable gases second and toxic gases third, with a calibrated direct-reading instrument, in the order 29 CFR 1926.1204(e) lists them. The reason for going first with oxygen is mechanical: a combustible-gas sensor needs oxygen to read correctly, so an oxygen-poor space can make an explosive one look harmless.
Flammables come before toxics because a fire or explosion at the opening reaches everyone near it, the attendant and the next trade over included, while a toxic gas mostly harms whoever breathes it. Toxics are measured last, against their permissible exposure limits.
Construction asks for more than a reading at the start. Under 29 CFR 1926.1204, monitoring during the entry is continuous where the equipment exists, which is stricter than the general-industry rule in 1910.146. How the competent person identifies spaces before work begins, and how they relate to trenches, is on excavation and confined spaces.
Below 19.5% is deficient. Above 23.5% is enriched, and things burn more readily. Normal air is about 20.9%
Flammable gas or vapor
Under 10% of the lower flammable limit
Lower flammable limit (LFL) and lower explosive limit (LEL) name the same point
Toxic gases
Below the permissible exposure limit
A level immediately dangerous to life or health (IDLH) is a hazardous atmosphere outright
Talking point 03
Three roles at the opening
Permit-space duties, 29 CFR 1926.1208 to 1926.1210scroll →
Duty
Entrant
Attendant
Entry supervisor
Position
Inside the space
Outside, for the whole entry
Where the job needs; may also act as attendant or entrant if trained
The permit
Works under it
Keeps count of who is inside
Checks tests and equipment, then signs it
Conditions change
Gets out when told or when an alarm sounds
Orders everyone out and summons rescue
Ends or suspends the entry
Rescue
Wears the retrieval harness
Non-entry rescue only
Confirms rescue services before entry
An attendant who climbs in becomes a second casualty and leaves no one outside to call for help.
Talking point 04
What turns a confined space into a permit space
A confined space is large enough to enter and work in, has limited ways in or out, and is not designed for continuous occupancy. Those three facts alone call for no permit. A permit is required when the space also holds a serious hazard: a hazardous atmosphere or the potential for one, material that could engulf an entrant, walls that converge or a floor that slopes down to a narrow section, or any other serious safety or health hazard (29 CFR 1926.1202).
Rescue is planned before the first entry. Non-entry retrieval is the default, set up before the first entrant goes in, and a rescue service that enters is the backup. The wider emergency side, from first aid kits to weather, is on first aid, rescue and weather.
Talking point 05
Permit-space set
These cards stay with permit spaces and the hazards around an entry. Ask what has to be true for anyone to go in, or to stay in, before you answer.
Card 1 of 6 · 0 right
Card 1
Workers will enter a 12-ft-deep vertical permit-required vault through a top manhole. Unless it would increase overall risk, what retrieval arrangement does 29 CFR 1926.1211 require?
Pick an answer. A short note for each option, A to D, appears here.
ACorrect: for vertical spaces more than 5 feet deep, a mechanical device must be available to lift an entrant attached by harness and retrieval line.
BA line tied to the ladder anchors the entrant but gives no way to lift an unconscious worker out.
CA second entrant adds another person to the hazard instead of providing non-entry rescue.
DAn attendant cannot reliably hand-haul an unconscious worker 12 feet, which is why a mechanical device is required.
Card 2
A superintendent has run three fire evacuation drills on a project that also has a permit-required confined space and a tower crane. What should the NEXT drill test?
Pick an answer. A short note for each option, A to D, appears here.
ARepeating a drill that already works refines a familiar scenario while higher-consequence emergencies stay untested.
BCorrect: drills should cover credible high-consequence scenarios, and a confined space rescue with the planned service tests a plan not yet exercised.
CAn unannounced fire drill adds realism but still tests the scenario that has been practiced three times.
DA tabletop with office staff leaves out the field crews and rescue service a real confined space emergency would involve.
Card 3
A crew will enter a tank that is connected by piping to a line carrying a flammable liquid. What is the MOST effective way to isolate the line before entry?
Pick an answer. A short note for each option, A to D, appears here.
AA closed, tagged valve can leak through or be opened by mistake, so it is a weaker form of isolation.
BCorrect: Blanking, blinding or removing a section of the line physically separates the tank, which is the most reliable isolation of a hazardous line.
CA watched valve still relies on a single closure that can leak, and the attendant has other duties during entry.
DStopping a pump does not stop gravity flow or pressure already in the line from reaching the tank.
Card 4
A storm knocks out temporary power while one crew works in a basement, another is on a scissor lift, and two entrants are inside a permit-required tank ventilated by an electric blower. What should the supervisor confirm FIRST?
Pick an answer. A short note for each option, A to D, appears here.
AWorkers on a stalled lift are stranded but not in immediate danger, so lowering them can follow the urgent step.
BCorrect: Loss of forced ventilation can create a hazardous atmosphere within minutes, a condition the permit does not allow, so entrants are ordered out first.
CRestoring power matters, but resetting the panel protects no one from the fastest-developing hazard.
DFlashlights help the basement crew, but darkness there is less urgent than a failing atmosphere in an occupied permit space.
Card 5
Entrants will clean a sewage lift station wet well that contains a pump set to start automatically on float level. Before entry, what should the supervisor verify?
Pick an answer. A short note for each option, A to D, appears here.
AAn attendant cannot react fast enough to protect an entrant once an automatic pump starts.
BCorrect: Permit-space entry requires isolation from hazards such as automatically starting equipment, and locking the disconnect, then trying to start the pump, confirms it.
CTying up the float is a control-circuit action that can slip or be undone, so it is not energy isolation.
DA selector switch is a control-circuit device that can be changed or bypassed, so it does not isolate the energy source.
Card 6
A crew working in a sewer manhole first notices a rotten-egg odor, and a few minutes later the odor seems to fade. How should the supervisor interpret this?
Pick an answer. A short note for each option, A to D, appears here.
AA fading odor can mean the concentration is rising, not dispersing.
BFading odor is not evidence of ventilation; only meter readings show whether the blower is working.
CNormal oxygen says nothing about toxic gases, which must be tested separately.
DCorrect: Hydrogen sulfide deadens the sense of smell, so odor is never a warning; a calibrated gas monitor is the only reliable guide.