46 CFR 16.105: Definitions for drug and alcohol testing terms

Last reviewed: October 14, 2026

This section defines terms used in this part, mostly for drug and alcohol testing. It covers who counts as a crewmember, what a marine employer is, and what operation includes. It also defines testing terms such as chemical test, MRO, service agent, and stand-down.

What it says

  1. A crewmember is an individual onboard a vessel acting under the authority of a credential issued under this subchapter, whether or not the individual is a member of the vessel's crew.

    46 CFR 16.105(1)“Onboard a vessel acting under the authority of a credential issued under this subchapter, whether or not the individual is a member of the vessel's crew; or”
  2. A crewmember also includes an individual engaged or employed onboard a vessel owned in the United States that is required by law or regulation to engage, employ, or be operated by a credentialed individual, except for the listed exclusions.

    46 CFR 16.105(2)“Engaged or employed onboard a vessel owned in the United States that is required by law or regulation to engage, employ, or be operated by an individual holding a credential issued under this subchapter”
  3. A marine employer is the owner, managing operator, charterer, agent, Master, or Person in Charge of a vessel, other than a recreational vessel.

    “Marine employer means the owner, managing operator, charterer, agent, Master, or Person in Charge of a vessel, other than a recreational vessel.”
  4. An employer means a marine employer or sponsoring organization.

    “Employer means a marine employer or sponsoring organization.”
  5. A dangerous drug is a narcotic drug, a controlled substance, or a controlled-substance analog, as defined in section 102 of the Comprehensive Drug Abuse and Control Act of 1970 (21 U.S.C. 802).

    “Dangerous drug means a narcotic drug, a controlled substance, or a controlled-substance analog (as defined in section 102 of the Comprehensive Drug Abuse and Control Act of 1970 (21 U.S.C. 802)).”
  6. A drug test is a chemical test of an individual's urine for evidence of dangerous drug use.

    “Drug test means a chemical test of an individual's urine for evidence of dangerous drug use.”
  7. Service agents are not employers for purposes of this part.

    “Service agents are not employers for purposes of this part.”
  8. A stand-down is the practice of temporarily removing a crewmember from safety-sensitive functions based only on a laboratory report to the MRO of a confirmed positive, adulterated, or substituted test, before the MRO has completed verification.

    “Stand-down means the practice of temporarily removing a crewmember from the performance of safety-sensitive functions based only on a report from a laboratory to the MRO”

Common questions

Who is a marine employer under 46 CFR 16.105?

A marine employer is the owner, managing operator, charterer, agent, Master, or Person in Charge of a vessel. Recreational vessels are excluded.

“Marine employer means the owner, managing operator, charterer, agent, Master, or Person in Charge of a vessel, other than a recreational vessel.”

What does it mean to fail a chemical test for dangerous drugs?

It means a chemical test conducted in accordance with 49 CFR 40 was reported as positive by a Medical Review Officer. The test must have shown a dangerous drug at or above the levels in 49 CFR part 40.

“was reported as “positive” by a Medical Review Officer because the chemical test indicated the presence of a dangerous drug at a level equal to or exceeding the levels established in 49 CFR part 40.”

What counts as a vessel owned in the United States?

It is any vessel documented or numbered under the laws of the United States. It also includes any vessel owned by a United States citizen that is not documented or numbered by any nation.

“any vessel documented or numbered under the laws of the United States; and any vessel owned by a citizen of the United States that is not documented or numbered by any nation.”

Is a service agent an employer under this part?

No. Service agents are not employers for purposes of this part.

“Service agents are not employers for purposes of this part.”

The text of 46 CFR 16.105

Electronic Code of Federal Regulations (eCFR), current as of April 16, 2026 · Read it on eCFR

Definitions of terms used in this part

Chemical test means a scientifically recognized test which analyzes an individual's breath, blood, urine, saliva, bodily fluids, or tissues for evidence of dangerous drug or alcohol use.

Consortium/Third party administrator (C/TPA) means a service agent who provides or coordinates the provision of a variety of drug and alcohol testing services to employers. C/TPAs typically perform administrative tasks concerning the operation of the employers' drug and alcohol testing programs. This term includes, but is not limited to, groups of employers who join together to administer, as a single entity, the DOT drug and alcohol testing programs of its members.

Credential is the same as defined in 46 CFR 10.107.

Crewmember means an individual who is:

(1) Onboard a vessel acting under the authority of a credential issued under this subchapter, whether or not the individual is a member of the vessel's crew; or

(2) Engaged or employed onboard a vessel owned in the United States that is required by law or regulation to engage, employ, or be operated by an individual holding a credential issued under this subchapter, except for the following:

(i) Individuals on fish processing vessels who are primarily employed in the preparation of fish or fish products, or in a support position, and who have no duties that directly affect the safe operation of the vessel;

(ii) Scientific personnel on an oceanographic research vessel;

(iii) Individuals on industrial vessels who are industrial personnel, as defined in this chapter; and

(iv) Individuals not required under part 15 of this subchapter who have no duties that directly affect the safe operation of the vessel.

Dangerous drug means a narcotic drug, a controlled substance, or a controlled-substance analog (as defined in section 102 of the Comprehensive Drug Abuse and Control Act of 1970 (21 U.S.C. 802)).

Drug test means a chemical test of an individual's urine for evidence of dangerous drug use.

Employer means a marine employer or sponsoring organization.

Fails a chemical test for dangerous drugs means that the result of a chemical test conducted in accordance with 49 CFR 40 was reported as “positive” by a Medical Review Officer because the chemical test indicated the presence of a dangerous drug at a level equal to or exceeding the levels established in 49 CFR part 40.

Marine employer means the owner, managing operator, charterer, agent, Master, or Person in Charge of a vessel, other than a recreational vessel.

Medical Review Officer (MRO) means a person who is a licensed physician and who is responsible for receiving and reviewing laboratory results generated by an employer's drug testing program and evaluating medical explanations for certain drug test results.

Operation means to navigate, steer, direct, manage, or sail a vessel, or to control, monitor, or maintain the vessel's main or auxiliary equipment or systems. Operation includes:

(a) Determining the vessel's position, piloting, directing the vessel along a desired trackline, keeping account of the vessel's progress through the water, ordering or executing changes in course, rudder position, or speed, and maintaining a lookout;

(b) Controlling, operating, monitoring, maintaining, or testing: the vessel's propulsion and steering systems; electric power generators; bilge, ballast, fire, and cargo pumps; deck machinery including winches, windlasses, and lifting equipment; lifesaving equipment and appliances; firefighting systems and equipment; and navigation and communication equipment; and

(c) Mooring, anchoring, and line handling; loading or discharging of cargo or fuel; assembling or disassembling of tows; and maintaining the vessel's stability and watertight integrity.

Passes a chemical test for dangerous drugs means the result of a chemical test conducted in accordance with 49 CFR part 40 is reported as “negative” by a Medical Review Officer in accordance with that part.

Positive rate for random drug testing means the number of verified positive results for random drug tests conducted under this part plus the number of refusals of random drug tests required by this part, divided by the total number of random drug test results (i.e., positives, negatives, and refusals) under this part.

Refuse to submit means you refused to take a drug test as set out in 49 CFR 40.191.

Serious marine incident means an event defined in 46 CFR 4.03-2.

Service agent means any person or entity that provides services specified under this part or 49 CFR part 40 to employers and/or crewmembers in connection with DOT drug and alcohol testing requirements. This includes, but is not limited to, collectors, BATs and STTs, laboratories, MROs, substance abuse professionals, and C/TPAs. To act as service agents, persons and organizations must meet the qualifications set forth in applicable sections of 49 CFR part 40. Service agents are not employers for purposes of this part.

Sponsoring organization is any company, consortium, corporation, association, union, or other organization with which individuals serving in the marine industry, or their employers, are associated.

Stand-down means the practice of temporarily removing a crewmember from the performance of safety-sensitive functions based only on a report from a laboratory to the MRO of a confirmed positive test for a drug or drug metabolite, an adulterated test, or a substituted test, before the MRO has completed verification of the test result.

Substance Abuse Professional (SAP) means a person who evaluates employees who have violated a DOT drug and alcohol regulation and makes recommendations concerning education, treatment, follow-up testing, and aftercare.

Vessel owned in the United States means any vessel documented or numbered under the laws of the United States; and any vessel owned by a citizen of the United States that is not documented or numbered by any nation.

Sections it refers to

The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of April 16, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.