Ontario trade codes and the Red Seal exam: 309A, 313A, 421A, 429A and 433A
Ontario names each skilled trade with a code, such as 433A for Industrial Mechanic Millwright. The code is Ontario’s, not a national Red Seal exam number. When you pass the certifying exam, Skilled Trades Ontario issues a Certificate of Qualification (C of Q), which people often call a 433A or 421A licence. All five trades below are part of the Interprovincial Red Seal Program in Ontario. Two are compulsory, so you need to be certified (or registered as an apprentice) to work in them.
The codes at a glance
309A: Electrician – Construction and Maintenance
- Red Seal trade: Construction Electrician
- Status in Ontario: Compulsory
- 9,000 hours (8,160 on the job and 840 in school)
Red Seal exam guide: Construction Electrician · Skilled Trades Ontario page (309A)
313A: Refrigeration and Air Conditioning Systems Mechanic
- Red Seal trade: Refrigeration and Air Conditioning Mechanic
- Status in Ontario: Compulsory
- 9,000 hours (8,280 on the job and 720 in school)
Red Seal exam guide: Refrigeration and Air Conditioning Mechanic · Skilled Trades Ontario page (313A)
421A: Heavy Duty Equipment Technician
- Red Seal trade: Heavy Duty Equipment Technician
- Status in Ontario: Non-compulsory
- 7,000 hours (6,280 on the job and 720 in school)
Red Seal exam guide: Heavy Duty Equipment Technician · Skilled Trades Ontario page (421A)
429A: General Machinist
- Red Seal trade: Machinist
- Status in Ontario: Non-compulsory
- 8,000 hours (7,280 on the job and 720 in school)
Red Seal exam guide: Machinist · Skilled Trades Ontario page (429A)
433A: Industrial Mechanic Millwright
- Red Seal trade: Industrial Mechanic (Millwright)
- Status in Ontario: Non-compulsory
- 8,000 hours (7,280 on the job and 720 in school)
Red Seal exam guide: Industrial Mechanic (Millwright) · Skilled Trades Ontario page (433A)
426A: Construction Millwright
- Red Seal trade: No Red Seal statement on its Skilled Trades Ontario page
- Status in Ontario: Non-compulsory
- 8,000 hours (7,280 on the job and 720 in school)
Compulsory or not: what a “433A licence” means
309A and 313A are compulsory trades. To work in them legally in Ontario you must hold a Registered Training Agreement, a Provisional Certificate of Qualification or a Certificate of Qualification, and your name must appear on the Skilled Trades Ontario Public Register. A C of Q in a compulsory trade must be renewed to stay valid.
421A, 429A and 433A are non-compulsory. Skilled Trades Ontario says this means you don’t have to be certified to work in the trade. You can still earn a C of Q by passing the certifying exam; it does not need renewal, and holders of non-compulsory certificates are not listed on the Public Register.
426A vs 433A: Construction Millwright and Industrial Mechanic Millwright
Ontario has two millwright trades. Industrial Mechanic Millwright (433A) is the Ontario name for the Red Seal trade Industrial Mechanic (Millwright). Construction Millwright (426A) lays out, receives and installs machinery and automated systems, and its Skilled Trades Ontario page does not list it under the Red Seal Program.
Both are non-compulsory, both set 8,000 apprenticeship hours (7,280 on the job and 720 in school), and the Level 1 and Level 2 curriculum standards posted on both pages are shared documents for 433A and 426A. Each trade has its own certifying exam and its own C of Q. Our Millwright app and guide follow the Red Seal Industrial Mechanic (Millwright) exam, which is the 433A route.
Millwright Red Seal exam: format, pass mark and how to prepare
421A vs 310T: Heavy Duty Equipment Technician and Truck and Coach Technician
These are two separate Ontario trades. A Heavy Duty Equipment Technician (421A) works on heavy duty equipment in sectors such as mining, construction, forestry, marine, transportation and materials handling. A Truck and Coach Technician (310T) inspects, repairs and maintains commercial trucks, emergency vehicles, buses and other road transport vehicles.
Both are Red Seal trades in Ontario: 421A under the Red Seal title Heavy Duty Equipment Technician, and 310T under the title Truck and Transport Mechanic. 421A is non-compulsory, with 7,000 apprenticeship hours (6,280 on the job and 720 in school). 310T is compulsory, so working in it requires a Registered Training Agreement, a Provisional Certificate of Qualification or a Certificate of Qualification; its apprenticeship is 6,720 hours (6,000 on the job and 720 in school).
The Level 1 in-school curriculum standard posted on both pages is a shared Commercial Vehicle and Equipment document. Each trade has its own certifying exam and its own C of Q. Our Heavy Duty Equipment Technician app and guide follow the Red Seal Heavy Duty Equipment Technician exam, which is the 421A route; they do not cover the Truck and Transport Mechanic exam.
Heavy Duty Equipment Technician (HDET) Red Seal exam guide: format, pass mark and how to prepare · Skilled Trades Ontario 310T page
Getting to the exam
Apprentices usually reach the certifying exam by finishing their Ontario apprenticeship. Experienced workers who did not complete an Ontario apprenticeship start with Skilled Trades Ontario’s Trade Equivalency Assessment. If it is approved, you can challenge the certifying exam, and after passing you pay a fee to receive the C of Q.
For these Red Seal trades, the Red Seal endorsement is the interprovincial standard added to the provincial certificate when you pass the Red Seal exam. Skilled Trades Ontario decides who may write, and sets fees and booking rules.
Questions about Ontario trade codes
What is the 433A trade in Ontario?
433A is Industrial Mechanic Millwright. In Ontario it is part of the Red Seal Program as Industrial Mechanic (Millwright). It is non-compulsory, and the apprenticeship is 8,000 hours.
Do I need a 433A or 421A licence to work in Ontario?
No. Industrial Mechanic Millwright (433A), Heavy Duty Equipment Technician (421A) and General Machinist (429A) are non-compulsory trades, so certification is optional. Electrician – Construction and Maintenance (309A) and Refrigeration and Air Conditioning Systems Mechanic (313A) are compulsory.
What is the difference between 426A and 433A?
433A Industrial Mechanic Millwright is the Red Seal trade Industrial Mechanic (Millwright). 426A Construction Millwright is a separate Ontario trade with its own certifying exam, and its Skilled Trades Ontario page does not list it as a Red Seal trade. Their Level 1 and 2 in-school curriculum is shared.
What is the difference between 421A and 310T?
421A Heavy Duty Equipment Technician works on heavy duty equipment such as mining, construction and forestry machines, and it is non-compulsory in Ontario. 310T Truck and Coach Technician works on commercial trucks, buses and other road vehicles, and it is compulsory. Both are Red Seal trades, with separate certifying exams: Heavy Duty Equipment Technician for 421A and Truck and Transport Mechanic for 310T.
Is 429A the Red Seal Machinist exam?
429A is Ontario’s General Machinist trade, which is part of the Red Seal Program under the title Machinist. The code is Ontario’s; other provinces use their own names and codes for the same Red Seal trade.
Is Red Seal Ready affiliated with Skilled Trades Ontario?
No. Red Seal Ready is an independent study app by Certloom Learning. It is not affiliated with or endorsed by Skilled Trades Ontario or the Red Seal Program. Check eligibility, fees and booking with Skilled Trades Ontario.
Official sources
Independent study aid by Certloom Learning. Not affiliated with or endorsed by Skilled Trades Ontario or the Red Seal Program. No passing guarantee.