The alcohol concentration limit for a Part 107 crewmember is 0.04. Section 107.27 applies §91.17, and you may not act as a crewmember with an alcohol concentration of 0.04 or greater. The concentration the rule allows is below 0.04. Below 0.10 borrows a different number. "Any level is acceptable" is not the rule.
The 0.04 limit is one of three alcohol limits
The concentration figure is easy to memorize and easy to isolate. It is not the only alcohol limit. Section 91.17 also prohibits acting as a crewmember within 8 hours after drinking and while under the influence. Those limits are separate. A person can be inside 8 hours with a concentration still under 0.04, and the time rule still applies. A person can be past 8 hours and at 0.04 or greater, and the concentration rule still applies. The 8-hour rule is the alcohol rules page. Refusing a test that would show the concentration is the refusal page.
On the knowledge test, the item asks for the maximum blood-alcohol concentration allowed to operate under Part 107. The correct choice is below 0.04 percent. Answer with that figure, not with a driving limit. Remember that "below 0.04" does not clear a crewmember who is still under the influence or still inside 8 hours.
Feeling legal is not the same as being fit
Section 107.17 is the fitness rule, and it is not a blood-alcohol paragraph. No person may manipulate the flight controls, or act as remote pilot in command, visual observer, or direct participant, if that person knows or has reason to know of a physical or mental condition that would interfere with the safe operation of the small unmanned aircraft system. The tested wording is the remote pilot version of that sentence: you may not act as remote pilot in command if you know or have reason to know of such a condition. "Have not eaten in two hours" is not the rule. Holding an FAA medical certificate is not the rule. Part 107 does not require a medical certificate. It requires you to stay off the controls when you know, or have reason to know, that you are not fit.
That is why a pilot who feels "legal" can still be grounded by §107.17. The 8 hours may have passed. The concentration may be under 0.04. If the pilot knows, or has reason to know, that fatigue, illness, or the residual effects of drinking would interfere with safe operation, §107.17 still says not to act as remote pilot, not to manipulate the controls, not to act as visual observer, and not to be a direct participant. Feeling under the number is not a finding that you are fit. The self-assessment is the point of the section. Nobody else issues a daily medical for this certificate.
A Saturday example makes the split obvious. Brunch included one drink at 9:00 a.m. The job is at 6:00 p.m., so the 8 hours have passed, and the pilot believes the concentration is under 0.04. By midafternoon the pilot is dizzy and slow. Section 91.17's clock may be satisfied and the concentration may be under the limit. Section 107.17 is not satisfied, because the pilot has reason to know of a condition that would interfere. The launch waits.
3P is the decision step after you notice it
The 3P model is Perceive, Process, Perform. It is an aeronautical decision-making tool. It is not part of §91.17, and it is not a synonym for the 0.04 limit. Perceive the hazard, including impairment you have noticed. Process the risk it poses to this flight. Perform by mitigating it or by not flying. The wrong expansions are Pilot, Passenger, Payload, and Prepare, Position, Proceed.
Use 3P after the notice, not instead of the regulation. You perceive that you are impaired, or that you have reason to think you are. You process what that does to the hover, the scan, and the go-around. You perform by refusing the crew role. Running 3P does not authorize a concentration of 0.04 or greater, and it does not shorten the 8 hours. It is how you act once §107.17 has already told you the condition matters. Drugs that impair faculties, including legal medicine, are a §91.17(a)(3) problem of their own on the medication page.
The trap is to treat 0.04 as the whole fitness code, or to treat 3P as if it were printed inside §91.17. The concentration limit is 0.04 or greater. Fitness is §107.17. The decision model, once you see the impairment, is Perceive, Process, Perform.
Run the concentration and fitness items on the free practice test. The lessons are at pricing.