HVAC technician screening questions: EPA 608, NATE, service versus install
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HVAC technician screening questions need to settle four things early: which EPA Section 608 certification type the candidate holds, whether they meet the state or local registration rules where the job is, whether their experience is service, installation or commercial maintenance, and whether they can diagnose a system rather than swap parts. Ask for the card, the setting and one recent diagnostic call in detail, and most mismatches show up inside ten minutes.
This page is specific to heating, ventilation, air conditioning and refrigeration work. The licensing ladder, the setting split and the safety questions for wiremen are on electrician screening questions, and plumbers are covered in plumber screening questions. For general call structure, use phone screen questions for recruiters.
The credentials, and what each one actually proves
HVAC resumes list a string of letters. Three are worth understanding before you get on the phone, checked on the issuers' own pages as of September 2026.
| Credential | What it is | What to ask |
|---|---|---|
| EPA Section 608 | Federal certification for technicians who maintain, service, repair or dispose of equipment that could release refrigerant. EPA lists four types: Type I for small appliances, Type II for high- and very high-pressure appliances, Type III for low-pressure appliances, and Universal for all types. EPA says the credentials do not expire. | Which type, which certifying organization issued the card, and can they send a photo. |
| NATE | A voluntary industry certification from North American Technician Excellence. NATE says certifications must be renewed every two years, through 16 continuing education hours or retaking the specialty exam, with a 120-day grace period. | Which specialty (for example air conditioning, gas heating, heat pumps), and the expiry date. NATE has a Verify a NATE ID lookup. |
| State or local license or registration | Set by each state, and sometimes by cities. Texas, for example, requires anyone who assists a licensed contractor with air conditioning and refrigeration work to register as a technician; Certified Technician is a voluntary higher designation that needs 24 months of supervised work or an approved training program plus an exam. California licenses HVAC contractors under the CSLB's C-20 classification. | What the job's state or city requires, then the candidate's registration or license number and expiry. |
The practical point on 608: EPA's refrigerant sales restriction limits who can buy refrigerant to certified technicians, with narrow exceptions. A technician without a 608 card cannot legally do much of the job a service company hires them for, and supply houses are expected to check for it. EPA does not issue the cards itself; the organization that ran the test does, so "I lost it, EPA has it on file" is not how it works. Ask which organization certified them.
Knockout questions
Ask these first. Confirm with the client which are fixed; an install helper order has different knockouts from a lead service tech.
| Question | What a strong answer sounds like | Red flags |
|---|---|---|
| Which EPA 608 certification do you hold, and who issued the card? | "Universal, through ESCO, I got it in trade school." Offers to text a photo. | "I'm certified" with no type. "I'm going to take it." For a service role, Type I only. |
| This job is in [state/city], which requires [registration/license]. Do you hold it, and when does it expire? | A number and a date, or "I'm registered in Texas, renewed in May." | A registration from another state, described as if it transfers. |
| This role is [residential service / new construction install / commercial maintenance]. How much of your last two years was that exact work? | Splits the time: "About 70 percent service calls, the rest change-outs." | "I do everything." The only matching work was an early helper job. |
| The role includes on-call [one week in four / weekends in peak season]. Can you take that rotation? | A plain yes, or a specific limit you can take to the client. | Yes, followed by a list of weekends they cannot work. |
| You would drive a company van and need a valid driver's license. Is yours current? | Yes, with any restriction that matters mentioned without prompting. | Unsure. The client's driving record check will settle it; note it and move on. |
| The client expects you to bring your own hand tools and provides [gauges, recovery machine, vacuum pump]. Does that work? | Knows what is in their kit and asks what the truck carries. | An experienced service tech with no tools of their own. |
Service, install or commercial: questions that separate them
A common reason HVAC placements fail is that the candidate's hours came from a different kind of work. An install tech who has set a hundred condensers may never have diagnosed a no-cool call alone, and a residential service tech may never have seen a chiller.
| Setting | What the work usually involves | A question that tests it |
|---|---|---|
| Residential service | Diagnosing and repairing split systems, furnaces and heat pumps in occupied homes, maintenance agreements, often presenting repair options to homeowners | "Walk me through your last no-cool call from the time you arrived." |
| Residential install | Change-outs and new construction: setting equipment, brazing line sets, pressure testing, evacuation, start-up | "On your last change-out, what did you do after brazing, before you released the refrigerant?" |
| Commercial service and maintenance | Rooftop units, split systems at larger tonnage, building automation, preventive maintenance routes, sometimes chillers and boilers | "What is the largest equipment you have worked on alone, and what controls system did the building run?" |
| Refrigeration | Walk-in coolers and freezers, reach-ins, ice machines, supermarket racks; often Type II work and urgent calls | "Tell me about a walk-in freezer that would not hold temperature. What did you find?" |
Experience questions with strong answers and red flags
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"Walk me through the last no-cool or no-heat call you ran on your own."
- Strong answer: an order: talked to the customer, checked the thermostat and power, looked at the filter and coils, took pressures and temperatures, worked out superheat or subcooling, found the cause, explained the options.
- Red flags: "I added refrigerant and it was fine," with no mention of looking for a leak. Or every story involves a senior tech who "figured it out".
-
"On an install, how do you know the system is ready to charge?"
- Strong answer: pressure testing with nitrogen, pulling a vacuum and reading it on a micron gauge, a decay test before opening the valves.
- Red flags: "We run the pump for a while." No gauge, no number, no test.
-
"Tell me about a refrigerant leak you found. How did you find it, and what did you do with the refrigerant?"
- Strong answer: an electronic detector or bubbles, the location, recovery into a cylinder with a recovery machine, the repair, and a note on the work order.
- Red flags: venting, or treating recovery as optional. That is a compliance problem for the client, not a style difference.
-
"Which equipment brands have you worked on most, and have you had any manufacturer training?"
- Strong answer: two or three brands, a factory class or a distributor course, and what it taught them.
- Red flags: none of the brands the client installs, for a role that expects day-one warranty work. Not a knockout, but worth telling the client.
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"How many calls did you typically run in a day in peak season, and who set your schedule?"
- Strong answer: a range, what drove it, and how dispatch worked. Service techs often mention a field service app by name.
- Red flags: a number far outside what the client's own techs run, in either direction. Ask what a typical call involved.
-
"Do you present repair options or sell replacements to homeowners? How are you paid for that?"
- Strong answer: clear about whether they sell, how they explain options, and whether they earned commission or spiffs.
- Red flags: a candidate who hates selling, for a client whose service techs are expected to generate replacement leads. Say so plainly and let them decide.
Commercial and controls questions
For commercial roles, the gap between the resume and the work is usually tonnage and controls.
| Question | What a strong answer sounds like | Red flags |
|---|---|---|
| What is the largest rooftop unit or split system you have serviced alone? | A tonnage and a building type: "Mostly 10 to 25 ton on strip malls, some 50 ton on a school." | Only residential tonnage, for a commercial service order. |
| Which building automation or controls systems have you worked with? | Names the systems and what they did in them: read alarms, changed setpoints, replaced sensors. | "I've seen it" for a role that expects them to troubleshoot controls. |
| Have you worked on chillers, cooling towers or boilers? In what role? | Specific equipment and whether they led or assisted. | "Chiller experience" that was holding a flashlight. |
| How do you document a preventive maintenance visit? | A checklist, readings recorded, photos, deficiencies written up for a quote. | No documentation habit, for a maintenance contract client. |
Safety, schedule and pay
| Question | What a strong answer sounds like | Red flags |
|---|---|---|
| What do you do before working on a unit's electrical components? | Shuts off and locks the disconnect, verifies with a meter before touching, knows capacitors can hold a charge. | "I just work around it." |
| Do you have an OSHA 10 or 30 card, and does the client's site require one? | A card type and year, or "No, but I can do it before the start date." | Claims a card they cannot describe. OSHA's Outreach program is voluntary awareness training, not a certification. |
| Peak season runs [10 to 12-hour days, some Saturdays]. What limits do you have? | A yes, or a specific limit. | "I'll make it work" with obvious hesitation. Ask what would make it hard, and stop if it turns personal. |
| The pay is [$X per hour, overtime after 40, on-call pay of $Y, commission on leads]. What do you need to make a move? | An hourly figure, plus how they weigh overtime, on-call and the van. | Only a headline rate, with no sense of hours in shoulder season. |
| Why are you leaving, or why did your last job end? | Trade-typical: seasonal layoff, wants commercial work, wants a take-home van or less on-call. | Several short stints ending the same way, with a different explanation each time. |
Ask what they need, not what they earn now; pay history questions are restricted in a number of states and cities. Wording is in salary expectation questions.
How HVAC experience gets overstated
- Helper time as technician time. Years carrying equipment and cleaning up counted as installing. Ask what they did alone.
- Install work described as service. Both are real skills. Only one is diagnosing a failure with the customer watching.
- Type I described as "608 certified". Type I covers small appliances. Ask the type every time.
- An expired NATE certification. NATE certifications lapse after two years without renewal. Ask the expiry date and check the NATE ID.
- Commercial by building, not by equipment. Residential-sized units on a small office roof are not the same as large rooftops and building controls.
- "Lead tech" with no one to lead. Ask how many people, and who ordered the parts.
Checklist before you submit
HVAC technician submittal checklist
- EPA 608 type and certifying organization recorded, with a photo of the card.
- State or local registration or license meets the job's location, with number and expiry.
- NATE specialty and expiry, if the client requires or pays for it.
- Hours in the client's setting (residential service, install, commercial, refrigeration), with the last date.
- One diagnostic story that includes measurements and a cause, not only a fix.
- Refrigerant recovery described correctly.
- Yes to on-call, peak-season hours, van and driving requirements.
- Pay expectation confirmed against the client's rate.
- Consent to submit for this client and this role, with the date.
General information, not legal advice. Certification and licensing rules differ by state and city and change over time. Confirm requirements with the licensing board where the work is done.
Describe the physical work and ask whether they can do it, with or without accommodation: "The job involves attics above 120 degrees in summer, roofs, ladders, and lifting condensers with a second person. Can you perform those duties, with or without accommodation?" Leave out health conditions, past injuries and workers' compensation claims; the EEOC's pre-employment guidance explains why. Criminal history belongs in the client's background check process, which is restricted before an offer in many places; see ban-the-box interview questions.
HVAC candidates often take screens from a job site between calls, and certification types, expiry dates and tonnage figures are the details that blur after a day of phone screens. Interview Signal runs on your computer's audio with no bot on the call, so the 608 type and the diagnostic story are in your notes the way the technician said them.
Questions people ask
Does EPA 608 certification expire?
No. EPA says Section 608 technician certification credentials do not expire. NATE certification is different: NATE says its certifications must be renewed every two years.
Which EPA 608 type does a residential HVAC technician need?
Residential split systems are generally high-pressure equipment, which is Type II; Type I covers small appliances such as window units and refrigerators. Most employers simply ask for Universal, which covers all equipment types, so confirm what the client's order says before you screen anyone out.
Is NATE certification required to work as an HVAC technician?
No. NATE is a voluntary industry certification. Some employers require or pay more for it, and state or local licensing is a separate question that depends on where the work is done.
How do I check an HVAC technician's certifications?
EPA does not issue 608 cards itself; the certifying organization that ran the test does, so ask for a photo of the card and the organization's name. NATE offers a Verify a NATE ID lookup on its site, and state boards such as Texas TDLR publish license and registration searches.