Ten free TSSA G3 practice questions.

Ten practice questions for the Ontario Gas Technician 3 (G3) exam, each with four options and one correct answer. TSSA's preparation guide says all its exam questions are multiple choice, apart from the power engineer exams. The G3 covers TSSA's nine modules: safety, fasteners and tools, the properties of propane and natural gas, codes, acts and regulations, electricity, manuals and drawings, customer relations, piping and tubing, and gas appliances. The questions are free to use, print and share. There is nothing to sign up for on this page.

01How to use these

The questions come from the TicketPrep G3 bank and follow TSSA's modules in order: Module 1 (safety), Module 2 (fasteners and tools), Module 3 (gas properties), Module 4 (codes, acts and regulations), Module 5 (electricity), Module 6 (manuals and drawings), Module 8 (piping and tubing), Module 9 (gas appliances). TSSA does not publish how many exam questions each module carries, so the ten are spread by our own estimate: two each from codes, acts and regulations and from piping and tubing, the two largest modules in our bank, and one each from six others. Customer relations (Module 7) is in the full bank. Two of the ten are calculations. Answer each one before opening the explanation. Every explanation covers all four options, because knowing why a wrong answer is wrong is most of the skill.

• Pace. TSSA does not publish the G3 question count or time limit; its preparation guide says its exams typically run 50 to 165 questions, with up to three and a half hours. Our timed mock exam gives 100 questions in 180 minutes, 1 min 48 s per question. Try these at that pace.
• Books. The exam is open book: you bring your own copies of the Technical Standards and Safety Act, 2000, the Fuels Regulations and their Code Adoption Documents, CSA B149.1 and CSA B149.2, with no writing or notes in them. The questions here put any figure they need in the question, so you can work them without the codes.
• Print. The printed version shows the questions and the answer key without the explanations, so it works as a handout. The explanations are on the web page. Print this page Download PDF
• Mark. TSSA's pass mark for Fuels exams, the G3 among them, is 75 percent. Eight of ten here clears that bar.

02The questions

1. Procedural · Module 1 · Safety

   During a furnace replacement in an occupied townhouse, the crew must hold the old furnace, packaging and tools somewhere until the end of the day. Where should they go?

   1. Clear of stairs, halls and exits, in the work area or outside
   2. In the front hall, close to the door, ready for quick removal later
   3. On the basement stairs, stacked tight against the wall
   4. In the utility room, stacked against the gas water heater
   Show the answer

   A. Correct. In an occupied home the family still needs its stairs, halls and doors, including as a way out in a fire. Keeping removed equipment, packaging and tools in the work area or outside keeps exits and walkways clear and free of trip hazards.

   Why not the others

   B. Equipment in the front hall blocks the main exit and is a trip hazard for the family. Keep exits and halls clear; hold material in the work area or outside.

   C. Anything on the stairs, even against the wall, narrows them, is a trip and fall hazard, and blocks the way out of the basement. Keep stairs clear.

   D. Packaging stacked against an operating water heater puts combustibles at the appliance and blocks access to it. Hold material in the work area away from appliances, or outside.

2. Procedural · Module 2 · Fasteners and tools

   A pipe cutter on 1/2 in. steel gas pipe now leaves a rough spiral track instead of a clean groove, and its cutting wheel has a visible nick. What is the right fix?

   1. file the nick smooth on the wheel
   2. replace the cutting wheel with a new one
   3. tighten the feed screw harder each turn
   4. oil the pipe and keep using the same wheel
   Show the answer

   B. Correct. A nicked or damaged cutter wheel will not track or cut cleanly, and safety guidance is to replace it. Use the wheel made for the material: a thin wheel for ordinary steel pipe, with other wheels for cast iron, stainless steel or plastic.

   Why not the others

   A. Filing changes the wheel's edge profile and leaves it uneven, so it still tracks badly; the wheel is a hardened cutting edge, not something dressed in the field. Replace a nicked wheel.

   C. Forcing the feed on a damaged wheel makes the spiral worse and can crush or flare the pipe end. The fault is the wheel, which is replaced.

   D. Lubricant helps a sound wheel cut but does nothing for a nick, which keeps throwing the wheel off its groove. Replace the damaged wheel.

3. Procedural · Module 3 · Gas properties

   On a cold morning, water drips from the cleanout at the base of an outside masonry chimney for the first few minutes after a natural-draft furnace starts, then stops as the chimney warms. Where does the water come from?

   1. Water driven out of the bricks as the hot flue gas dries the masonry
   2. Rain or snow that entered the chimney top overnight, now draining
   3. Moisture carried in the natural gas supply and released in the flame
   4. Water vapour from the burning gas, condensing on the cold chimney
   Show the answer

   D. Correct. Burning natural gas forms a large amount of water vapour from the hydrogen in the fuel. While the chimney walls are below the flue gas's dew point, that vapour condenses on them; once they warm up, it leaves as vapour.

   Why not the others

   A. Drying bricks would give off vapour, not run liquid water out of the cleanout at every cold start. The flue gas's own water vapour is condensing.

   B. Rain or melting snow would not start and stop with the furnace's warm-up. The timing points to flue gas cooling below its dew point on cold masonry.

   C. Pipeline gas is dry: the distributor gives its water content as typically 16 to 32 mg/m³. The water comes from combustion itself, as the hydrogen in the gas burns to water vapour.

4. Recall · Module 4 · Codes, acts and regulations

   A gas piping fitter (GP certificate) has run new piping to a replacement furnace in a detached house, tested it and connected it to the furnace. The owner asks him to light and adjust the furnace too. Under O. Reg. 215/01, may he?

   1. Yes; connecting the piping brings the whole appliance into the GP's scope
   2. No; a GP's scope covers the piping and its connection, not the appliance
   3. Yes, provided the furnace input is 400 000 Btuh (117 kW) or less
   4. Only once he has completed the pressure test tag for the piping
   Show the answer

   B. Correct. O. Reg. 215/01 s. 29 lets a GP install, alter, purge, test and repair gas piping and tubing, connect it to new or replacement appliances, and install venting, but not activate or service the appliance. Lighting and adjusting the furnace is G.2 work (400 000 Btuh (117 kW) or less) or G.1 work.

   Why not the others

   A. Section 29(2) lets a GP connect piping to a newly installed or replacement appliance, but that does not extend the certificate to the appliance itself; activating and adjusting it need a G.2 or a G.1.

   C. 400 000 Btuh (117 kW) or less is the G.2's appliance limit (s. 21(1)). The GP certificate covers piping, connections and venting, not work on the appliance at any input.

   D. Completing the test tag finishes the piping work; it does not authorize appliance work. Activating and adjusting the furnace lie outside the GP's scope in s. 29.

5. Recall · Module 4 · Codes, acts and regulations

   Ontario adds CSA 6.19-17 (residential carbon monoxide alarms) and the two gas clothes dryer standards to B149.1-25 so that its clauses can call them up. Which part of the code receives them?

   1. The reference publications section
   2. The definitions section
   3. Annex Q, the residential boiler checks
   4. The appliance section's dryer clauses
   Show the answer

   A. Correct. FS-279-26 amends Section 2, the list of reference publications, by adding CSA 6.19-17, the two dryer standards and others. Other clauses, such as Ontario's boiler and CO-alarm rules and the dryer certification clauses, then cite them.

   Why not the others

   B. Section 3 defines terms; Ontario changes it for appliance, approved, authority having jurisdiction and the dryer classes. The standards themselves are listed in Section 2, reference publications.

   C. Annex Q requires CO alarms certified to CSA 6.19-17, but it is not where the code lists the standards it refers to. Those are added to Section 2.

   D. Ontario's dryer clauses in Section 7 require certification to the dryer standards, but the standards are listed as reference publications in Section 2.

6. Calculation · Module 5 · Electricity

   A hot-surface igniter with a hot resistance of 45 Ω is fed at 120 V, and a loose crimp at its plug adds 3 Ω in series. What current flows through the igniter?

   1. 2.50 A
   2. 2.67 A
   3. 2.86 A
   4. 40.0 A
   Show the answer

   A. Correct. Series resistances add: 45 + 3 = 48 Ω, so I = 120 V ÷ 48 Ω = 2.50 A. The crimp also drops 2.50 × 3 = 7.5 V and heats, so the igniter runs cooler and the connection can burn.

   Why not the others

   B. This ignores the crimp: 120 ÷ 45 = 2.67 A. The 3 Ω is in series and adds to the total: 120 ÷ 48 = 2.50 A.

   C. This subtracts the crimp's resistance: 120 ÷ (45 − 3) = 2.86 A. Resistances in series add, so the total is 48 Ω and the current 2.50 A.

   D. This divides the voltage by the crimp alone: 120 ÷ 3 = 40.0 A. The crimp and igniter are in series, so the current is set by the total 48 Ω: 2.50 A.

7. Recall · Module 6 · Manuals and drawings

   A drawing of a basement shows the gas piping in a plan (top) view and in a front elevation. In which view can the height of the vertical drop to the furnace be read?

   1. either view, as each shows all three dimensions
   2. the plan view
   3. the front elevation
   4. neither view; only an isometric shows heights
   Show the answer

   C. Correct. Each orthographic view shows two of the three dimensions: a plan shows length and width as seen from above, while an elevation shows length and height. A vertical drop appears at its true length only in an elevation.

   Why not the others

   A. Each orthographic view shows only two dimensions, which is why a drawing needs more than one view. The plan shows length and width; the drop's height is read in the elevation.

   B. From above, a vertical drop is seen end-on as a point or small circle, so its height cannot be read in plan. Heights are read in an elevation such as the front view.

   D. Orthographic elevations show heights directly; an isometric is one way to show them, not the only way. Read the drop's height in the front elevation.

8. Procedural · Module 8 · Piping and tubing

   A range's gas inlet is a 1/2 in. male NPT nipple, and the new certified connector ends in flare nuts. How is the connector attached at the range?

   1. Through a union screwed onto the nipple, with the flare nut made up to the union's tail
   2. Directly, threading the connector's flare nut onto the nipple with gas-rated sealant
   3. Through a flare adapter on the nipple, with the flare nut made up on the adapter
   4. Through a compression adapter, with a brass ferrule slid over the connector's end
   Show the answer

   C. Correct. A connector's flare nut seals on a flare seat, not on pipe threads, and the connector maker warns against assembling it directly onto male pipe threads. A flare adapter (female pipe thread to male flare) goes on the nipple with gas-rated sealant on the nipple's threads, and the flare nut is tightened on the adapter with no sealant on the flare.

   Why not the others

   A. A union joins two pipe ends; it does not provide the flare seat the connector nut needs. The correct part is a flare adapter, threaded onto the nipple, that the flare nut tightens onto.

   B. A flare nut has a straight thread made to pull a flare onto a seat; it is not a tapered pipe thread and will not seal on one, with or without sealant. The connector maker forbids fitting the nut directly to male pipe threads.

   D. A connector's end is a flare nut, not plain tube for a ferrule, and a compression joint is not how a certified connector is attached. The nut goes onto a flare adapter fitted to the nipple.

9. Calculation · Module 8 · Piping and tubing

   A townhouse has a boiler whose rating plate shows 90 000 Btuh (26.4 kW) input and 78 000 Btuh (22.9 kW) output, and a range rated 55 000 Btuh (16.1 kW) input. What load is used to size the gas piping that serves both?

   1. 133 000 Btuh (39.0 kW)
   2. 145 000 Btuh (42.5 kW)
   3. 159 000 Btuh (46.6 kW)
   4. 223 000 Btuh (65.4 kW)
   Show the answer

   B. Correct. Piping is sized for the gas the appliances burn, which is their rated input: 90 000 + 55 000 = 145 000 Btuh (42.5 kW). The boiler's output (78 000 Btuh) is the part of that input that reaches the heating water after flue and jacket losses.

   Why not the others

   A. This uses the boiler's output: 78 000 + 55 000. Output is the heat delivered to the water; the gas the burner must receive is set by its input, so the load is 90 000 + 55 000 = 145 000 Btuh.

   C. This treats the 90 000 Btuh input as if it were an output and divides by the efficiency again: 90 000 ÷ (78 000 ÷ 90 000) = 103 800, plus 55 000 = 158 800, about 159 000. The input on the plate is already the gas burned: 145 000 Btuh.

   D. This adds every figure on both plates: 90 000 + 78 000 + 55 000 = 223 000. The output is not a second load; it is the share of the input that reaches the water. Add the inputs only: 145 000 Btuh.

10. Procedural · Module 9 · Gas appliances

    Working beside a G.2, a G.3 is asked to read a furnace's manifold pressure and compare it with the rating plate. Where and when is the manometer reading taken?

    1. At the drip leg's cap, with all the house's appliances firing
    2. At the gas control's inlet pressure tap, with the burner off
    3. At the gas control's outlet pressure tap, with the burner off
    4. At the gas control's outlet tap, with the main burner firing
    Show the answer

    D. Correct. Manifold pressure is the pressure downstream of the regulator, so it is read at the control's outlet tap, and only with the main burner lit (the kit instructions run the furnace about three minutes first) does the reading show what the regulator delivers to the orifices.

    Why not the others

    A. The drip leg is on the supply piping upstream of the appliance. A reading there is a supply pressure under load, which helps judge the piping, but it is not the pressure in the burner manifold.

    B. The inlet tap with the burner off gives the static supply pressure. That is a useful reading, but it is the pressure upstream of the regulator, not the manifold pressure the rating plate states.

    C. With the burner off the automatic valve is closed and no gas flows through the regulator, so the outlet side shows nothing about the working manifold pressure. The reading is taken with the main burner firing.

03Answer key

04More free questions

For the exam itself, the TSSA G3 exam guide covers the nine modules, the format, the fees and what you may bring into the room, and the TSSA G3 practice test page has five more sample questions and describes the full TicketPrep G3 bank. Each module also has five free questions of its own: Module 1, Module 2, Module 3, Module 4, Module 5, Module 6, Module 7, Module 8, Module 9. The same free format covers other trades too, including the ones that work with gas piping and appliances.

How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it. TicketPrep is an independent study site; it is not affiliated with TSSA (Technical Standards and Safety Authority) or CSA Group, and nothing here is taken from the exam, the TSSA curriculum, the CSA training units or the code text.