Can you drug test HVAC and plumbing techs, and what about marijuana?

A drug testing policy names the moments when you test.

For HVAC and plumbing shops the list usually has three entries.

Pre-employment: an applicant tests before their first day.

Random: current employees can be selected for an unannounced test on a schedule you set.

Post-accident: a test is triggered by an incident on the job.

Deciding which of these your policy covers — and writing down how each one works — is the first drafting decision you will make.

For techs driving standard service vans, there is no federal testing program behind any of the three: the occasions your policy covers, and what a positive result lets you do about it, are governed by your state's employment law.

State marijuana and cannabis employment protections vary, and some states limit pre-employment THC testing specifically.

Our research covered the federal rules and that principle; it did not produce a verified state-by-state list.

So before any occasion goes into the policy, check how your state's current law treats it — that one check applies to all three.

Testing is one layer of the screen, not the whole screen.

The criminal-history layer runs on its own rules — our guide to the background check HVAC technician applicants get covers the consent and adverse-action steps that process requires.

Keep the two policies as separate documents: they answer different questions, and a mixed-up screen is harder to defend.

If any of your drivers are DOT-tested, a separate federal program applies to them — the section below covers when that happens.

The direct answer: state marijuana and cannabis employment protections vary, and some states limit pre-employment THC testing — but we will not name the states, because our research did not verify a state-by-state list.

Naming the wrong state on an employment-law page is worse than a short answer, so this page stays at the level we can support.

Practically, that principle means you cannot assume a THC panel is safe to run in every state just because it is common across the trades.

Before your policy or your application packet names marijuana, check your state's current employment law — your state legislature's website or an employment attorney can tell you whether pre-employment THC testing is limited, and how far the protection reaches.

Date-stamp whatever you find and keep it with the policy file: an employment-law answer has a shelf life, and a policy drafted years ago can drift out of step with the law.

In the marijuana-law discussion, "safety-sensitive" is the label for roles where a state might narrow its protections — the theory being that impairment in some jobs endangers more than the worker.

Whether HVAC and plumbing tech work fits that label is exactly the question, and it is one our research cannot answer: we did not verify how any state defines safety-sensitive work, or whether techs who handle refrigerant, gas lines or live electrical work qualify for an exemption.

We will not guess at a definition that consequential — read the statute itself.

One related boundary is solid, because it is federal: drivers subject to CDL requirements sit under a drug and alcohol testing program of their own, covered in the next section.

For everyone else, treat the safety-sensitive question as part of the same state-law check as the THC limits in the section above — one read of your state's statute, or one conversation with an employment attorney, covers both.

Ask specifically how the law treats safety-sensitive roles, and get the answer in writing before you rely on an exemption.

DOT drug and alcohol testing is not a policy you adapt — it is a federal program, 49 CFR part 382, and it applies to employers of drivers who are subject to CDL requirements.

A driver who does not need a CDL is not a DOT-tested driver: for a standard service van, this program never arrives.

The question that decides it for your fleet is which vehicles create a CDL requirement.

The federal thresholds are weight-based.

Class B covers single vehicles with a GVWR of 26,001 pounds or more; Class A covers combinations of 26,001-plus pounds GCWR towing more than 10,000 pounds.

Typical HVAC and plumbing service vans sit well under 26,001 pounds — no CDL, and no DOT testing.

Watch the combination trap: a van towing a trailer is judged on the combination rating (GCWR), so a tow rig can cross a line the van alone never would.

Check box trucks and tow rigs against these thresholds before you assume the whole fleet is CDL-free.

Two other DOT numbers come up in the same conversation, and neither one is drug testing.

At 10,001 pounds GVWR or GCWR in interstate commerce, a vehicle is a commercial motor vehicle, and FMCSA requires companies operating such vehicles to register and carry a USDOT number.

FMCSA's list also counts 37 states plus Puerto Rico — including California, Texas, Florida, New York and Pennsylvania — that require a USDOT number for intrastate commercial vehicles, with intrastate weight thresholds varying by state.

A USDOT number on the door does not put a tech under DOT drug testing; the testing program follows the CDL, not the registration.

The takeaway for a contractor: unless you run heavy trucks or tow rigs that cross the Class thresholds, none of your techs are DOT-tested, and your written policy is the whole program.

Where driving records still matter — and they matter to your fleet insurer — the MVR check for employees is the screen that covers them.

Confirm each vehicle's ratings against FMCSA's current rules when you add a truck.

A straight answer about what we know: the research for this page covered the DOT program and the state-law principle around marijuana testing.

It did not verify OSHA's current position on post-accident drug testing — what the agency permits, restricts or discourages when an employer tests after an incident.

Our research notes point to OSHA's recordkeeping rule at 29 CFR 1904.35 as where post-incident testing is addressed, but we have not verified the rule's text and will not summarize a rule we have not read.

Before you write an automatic post-accident testing clause — or act under one — read the current rule on osha.gov, or put the question to an employment attorney who works in your state.

Post-accident testing is one clause in a much wider stack: sourcing, screening, pay, onboarding.

Our guide to hiring HVAC and plumbing techs covers the rest of it.

Whatever your state law, the DOT program and OSHA's rules turn out to allow, put what you decide in writing, apply it the same way to every employee, and date it — a policy that lives only in the owner's head fails exactly when it is needed most.

This page is employer career and business information, not legal advice. The vehicle-weight and testing rules summarized here are FMCSA regulations, marijuana testing protections are state law, and OSHA's position sits in its recordkeeping rules — confirm what applies to your company with the relevant agency, and have an employment attorney review your drug-testing policy.