How long does it take to get a 313D licence?

Through an apprenticeship, STO sets 4,500 hours of training, about two and a half years: 4,020 hours on the job and 480 hours in school over two levels, then the certifying exam. Experienced workers can apply for a Trade Equivalency Assessment instead and, if approved, go straight to the exam.

Can I challenge the 313D exam?

Yes, if STO's Trade Equivalency Assessment approves you. It costs $235 + HST and looks for trade experience at least equal to the apprenticeship's 4,500 hours. You then write the same certifying exam as apprentices, for $150 + HST.

How much does the 313D licence cost?

The certifying exam is $150 + HST, and the yearly C of Q renewal is $60 + HST. A Trade Equivalency Assessment, for the challenge route, is $235 + HST. The ODP card's course fee is set by the course provider.

Can a 313D mechanic work on gas furnaces?

Not on the gas side with the 313D alone. On our reading of O. Reg. 875/21, which is not legal advice, the C of Q does not authorize work needing a Technical Standards and Safety Act certificate, so gas work needs a TSSA gas technician certificate such as a G3 or G2.

How to Get Your 313D License in Ontario

The 313D "licence" is Skilled Trades Ontario's Certificate of Qualification (C of Q) in Residential Air Conditioning Systems Mechanic, a compulsory trade: to work in it you need a registered training agreement, a provisional C of Q or a C of Q. There are two ways to the certificate. Apprentices complete 4,500 hours of training, 4,020 on the job and 480 in school over two levels, then write the certifying exam. Experienced workers who did not apprentice in Ontario apply for a Trade Equivalency Assessment ($235 + HST) and, if approved, challenge the same exam ($150 + HST, 70 per cent to pass). The C of Q is renewed every year ($60 + HST), and you also need an ODP card to service refrigeration equipment. 313D is not a Red Seal trade.

4,500 hApprenticeship: 4,020 on the job + 480 in school

$235 + HSTTrade Equivalency Assessment (challenge route)

$150 + HSTCertifying exam fee, 70% to pass

$60 + HSTYearly C of Q renewal

Try free 313D questions Get all 550 – $69

01What is a 313D licence?

What most people call a 313D licence is the Certificate of Qualification that Skilled Trades Ontario (STO) issues in the trade of Residential Air Conditioning Systems Mechanic, trade code 313D. The trade is compulsory under the Building Opportunities in the Skilled Trades Act, 2021 and O. Reg. 876/21. STO's trade page says that to practise it legally in Ontario a person must hold a registered training agreement, a provisional Certificate of Qualification or a Certificate of Qualification, and appear on STO's Public Register.

313D is not a Red Seal trade. It is an Ontario-only certificate for residential air conditioning and heat pump systems. Its sister trade, 313A Refrigeration and Air Conditioning Systems Mechanic, covers the full trade and is the Red Seal one; if you are deciding between them, read 313A vs 313D.

02What does a 313D licence let you work on?

The scope is set in law, in O. Reg. 875/21 s. 119(1). It gives 313D the same scope as the 313A trade, "but is limited to" residential air conditioning systems that meet two requirements:

"The system must be installed as an independent unit in a residential family dwelling."
"The system must operate at no more than 240 volts single phase power with a maximum branch circuit capacity of 60 amps, a maximum cooling capacity of 60,000 British thermal units per hour and a saturated suction temperature above 2 degrees Celsius (35 degrees Fahrenheit) in the cooling cycle."

Section 119(2) takes out the repair or installation of portable, self-contained plug-in appliances of up to 240 volts that come precharged from the factory: that work is outside the trade's scope. And s. 116(3), which applies to 313D through s. 119, says a Certificate of Qualification does not authorize work for which a certificate is needed under the Technical Standards and Safety Act, 2000. That is where gas work comes in (see below).

In practice: split air conditioners, ducted and ductless heat pumps in a house, inside the 240 volt, 60 amp and 60,000 Btu/h limits. Three-phase equipment, larger systems, commercial refrigeration and anything running below a 2 degree Celsius saturated suction are outside 313D.

03Route 1: the 313D apprenticeship

STO sets the training for the trade at 4,500 hours, about two and a half years: 4,020 hours of on-the-job experience and 480 hours of in-school training, in two levels. The academic entry requirement is Grade 10, under O. Reg. 877/21.

Find a sponsor. An employer who will train you signs a training agreement with you, and once it is registered you are an apprentice and may work in the trade.
Log the skills. As you learn each skill on the job, your sponsor or trainer signs it off in the trade's training standard.
Do the two school levels. Depending on the school, in-school training runs as block release, day release, part-time or another delivery. Level 1 is a common core shared with 313A; Level 2 is 313D's own, with psychrometrics, heat load calculations, residential AC systems, air distribution and residential electrical and control systems.
Write the certifying exam. With the apprenticeship complete, you book STO's certifying exam.

04Route 2: the Trade Equivalency Assessment and the 313D challenge exam

If you have worked in the trade but did not complete an Ontario apprenticeship, STO's Trade Equivalency Assessment is the first step. It decides whether you may challenge the certifying exam. STO looks for experience in the trade at least equal to the apprenticeship's total training time, on the job and in school together, which for 313D is 4,500 hours. The assessment costs $235 + HST, and if it is turned down you can apply for a reassessment with new documents and a reassessment fee.

If you are approved, you write the same certifying exam as apprentices. There is no separate challenge exam: "challenging" just means writing it without having apprenticed in Ontario.

05The certifying exam

STO sets and delivers the 313D exam. You pay the fee of $150 + HST in your STO Portal account and book a sitting; since February 1, 2026 STO runs the exams itself, at STO exam centres and some training sites, on paper or on screen. The pass mark is 70 per cent. STO publishes no question count for 313D, only that its exams have between 90 and 150 multiple-choice questions and up to four hours. Results come within 15 business days, and if you do not pass you wait 30 days and pay the fee again before you rewrite.

The format, the six weighted skill sets and how to prepare are in the 313D exam guide. To see where you stand, try the free questions on the 313D practice exam page.

06After you pass: the C of Q and its renewal

Once you pass, STO issues your Certificate of Qualification, and you appear on its Public Register. In a compulsory trade the certificate must be renewed to stay valid: STO's Certificate of Qualification page gives an annual fee of $60 + HST, and after each renewal you get an expiry sticker for your wallet card and the Public Register shows the new date.

07You also need an ODP card

A C of Q does not replace the refrigerant card. Ontario's O. Reg. 463/10 s. 22(1) says: "No person shall service or test refrigeration equipment that contains a refrigerant unless the person is certified under section 34". That certification is the Ozone Depletion Prevention (ODP) card, which you get after a one-day course and which is valid for five years. The province's refrigerant certificate page adds that the ODP card on its own does not let you work on refrigeration equipment as a mechanic. You need both.

08Can a 313D work on gas furnaces?

Not on the gas side, on the 313D licence alone. Section 116(3) of O. Reg. 875/21, carried over to 313D by s. 119, says the C of Q does not authorize work that needs a certificate under the Technical Standards and Safety Act, 2000, and gas work does: it falls under TSSA's gas technician certificates in O. Reg. 215/01, from the G3 up to the G2, which covers appliances of up to 400,000 Btu/h. The 313D training standard lists a gas technician certificate as optional training and has no furnace or gas content of its own. So a furnace can be the air handler for a 313D's cooling coil, but servicing its burner, gas valve or venting needs a gas ticket.

That is our reading of the regulations, not legal advice; check with TSSA for your own work. If you are starting the gas side, see the TSSA G3 practice test.

09Moving on to 313A later

313D and 313A share their Level 1 in-school common core, and STO built the 2023 313D training standard in parallel with 313A's for, in its words, "a smoother transition" between the residential and the full trade. STO publishes no rule we could find that credits 313D hours or the 313D certificate toward 313A, so ask STO before you plan on one. 313A vs 313D compares the two trades side by side.

10Questions people ask

How long does it take to get a 313D licence?: Through an apprenticeship, STO sets 4,500 hours of training, about two and a half years: 4,020 hours on the job and 480 hours in school over two levels, then the certifying exam. Experienced workers can apply for a Trade Equivalency Assessment instead and, if approved, go straight to the exam.
Can I challenge the 313D exam?: Yes, if STO's Trade Equivalency Assessment approves you. It costs $235 + HST and looks for trade experience at least equal to the apprenticeship's 4,500 hours. You then write the same certifying exam as apprentices, for $150 + HST.
Do I need a licence to do residential AC work in Ontario?: Yes. 313D is a compulsory trade, so STO says you must hold a registered training agreement, a provisional Certificate of Qualification or a Certificate of Qualification, and appear on its Public Register. Servicing refrigeration equipment also needs an ODP card under O. Reg. 463/10.
Is 313D a Red Seal licence?: No. 313D is an Ontario-only Certificate of Qualification. The Red Seal trade is 313A Refrigeration and Air Conditioning Systems Mechanic, the full trade, which needs 9,000 hours of training against 313D's 4,500.
How much does the 313D licence cost?: The certifying exam is $150 + HST, and the yearly C of Q renewal is $60 + HST. A Trade Equivalency Assessment, for the challenge route, is $235 + HST. The ODP card's course fee is set by the course provider.
Can a 313D mechanic work on gas furnaces?: Not on the gas side with the 313D alone. On our reading of O. Reg. 875/21, which is not legal advice, the C of Q does not authorize work needing a Technical Standards and Safety Act certificate, so gas work needs a TSSA gas technician certificate such as a G3 or G2.

11Sources

Skilled Trades Ontario: Residential Air Conditioning Systems Mechanic: compulsory status, the 4,500 hours (4,020 on the job, 480 in school), the two levels, delivery options and renewal. Accessed November 1, 2026.
STO: Trade Equivalency Assessment: the challenge route, the experience required, reassessment and the $235 + HST cost. Accessed November 1, 2026.
STO: Exam scheduling: the $150 + HST exam fee and the 30-day wait before a rewrite. Accessed November 1, 2026.
STO: Certificate of Qualification: the $60 + HST annual fee for compulsory trades and the wallet-card expiry sticker. Accessed November 1, 2026.
STO: 313D Apprenticeship Training Standard, December 4, 2023 (PDF): optional certifications, including gas technician and ODP, and the general exam details. Accessed November 1, 2026.
O. Reg. 875/21, Scopes of Practice (e-Laws): s. 116(3) and s. 119. Accessed November 1, 2026.
O. Reg. 877/21, General (e-Laws): the Grade 10 academic entry requirement for the trade. Accessed November 1, 2026.
O. Reg. 463/10, Ozone Depleting Substances and Other Halocarbons (e-Laws): s. 22(1). Accessed November 1, 2026.
Ontario: Get a certificate to handle refrigerants: the ODP card, its one-day course and five-year term. Accessed November 1, 2026.

Read on Skilled Trades Ontario's pages and Ontario e-Laws on November 1, 2026. The quotations are from Ontario regulations, which may be reproduced; STO's training standard and curriculum are used only for what they cover. The section on gas work is our reading of the regulations, not legal advice. STO and TSSA are the final word on their certificates; if you find something here out of date, tell us.

12Practice for this exam

Getting ready for the 313D certifying exam, by apprenticeship or as a challenge? TicketPrep's 313D practice exams cover all six skill sets on STO's counselling sheet with every option explained, and the timed mocks are 130 questions in four hours. Exam Pass is $69 one time for 120 days, and All-Access at $119 includes 313D, 313A and every other exam on the site.

Ten free questions per trade, no account: free practice questions. How our questions are written and checked: how our questions are made.