Chapter 2b: Air Supply Subsystem

The “Air Supply Subsystem” chapter is a key focus in the Ontario air brake practice test, designed to help drivers understand how air is supplied and managed within air brake systems.

Ontario Air Brake Test - Chapter 2b: Air Supply Subsystem

1 / 25

What is a wig wag in an air brake system?

A type of alcohol evaporator

A component of the air dryer

A type of safety valve

A warning device whose arm drops into the driver’s view when pressure is too low

2 / 25

What is the function of safety valves in an air brake system?

To cool the compressor

To dry the air

To increase braking force

To prevent over-pressure of the system

3 / 25

Why must vehicles with air brakes have working air pressure gauges?

To monitor battery voltage

To display engine speed

To measure coolant temperature

To show how much air pressure is in the system and ensure normal operation

4 / 25

What units of measurement may air pressure gauges display?

Volts and amps

Litres and gallons

Celsius and Fahrenheit

kPa and psi

5 / 25

What is one function of an alcohol evaporator in the air brake system?

To lubricate the compressor

To help prevent moisture in the system from freezing

To increase brake application speed

To reduce air tank volume

6 / 25

What should you do if the low air-pressure warning activates?

Recognize it as a serious hazard and bring the vehicle to a safe stop as soon as possible

Ignore it if the vehicle seems to brake normally

Increase engine speed to build pressure faster and continue driving

Pump the brakes repeatedly to test the system

7 / 25

What type of warning must all low air-pressure warning devices provide?

An engine shutdown

A vibration in the brake pedal

A change in steering feel

A visual warning, such as a light

8 / 25

What is the main purpose of an alcohol evaporator in an air brake system?

To add alcohol vapour that mixes with moisture and reduces freezing

To cool the air compressor

To increase overall air pressure

To lubricate brake components

9 / 25

What do some vehicles use to show primary and secondary air-tank pressure?

Only a digital display

Two separate gauges or one gauge with two needles

Only one gauge with one needle

A warning buzzer

10 / 25

What do air pressure gauges in the cab indicate?

Pressure in the tires

Air pressure in the primary and secondary air tanks

Air temperature in the engine compartment

Pressure in the cooling system

11 / 25

What is the purpose of an air dryer in an air brake system?

To cool the compressed air for better performance

To increase system pressure above normal levels

To filter engine oil

To remove moisture from the system and expel it at compressor cut-out

12 / 25

Is it safe to drive when air pressure is outside the normal operating range?

Yes, if the load is light

No, it is unsafe to drive in that condition

Yes, but only at low speeds

Yes, as long as the brakes feel normal

13 / 25

What is the normal operating pressure range for vehicle air brake systems?

Between 1000 kPa and 1380 kPa (145 psi and 200 psi)

Between 200 kPa and 400 kPa (30 psi and 60 psi)

Between 552 kPa and 1000 kPa (80 psi and 145 psi)

Between 275 kPa and 550 kPa (40 psi and 80 psi)

14 / 25

Where might compressed air exhaust from an air brake system?

Only from the compressor intake

Only from the engine tailpipe

Exhaust ports of brake valves, near axles, air-dryer exhaust, and tank drain valves

Only from the dashboard controls

15 / 25

How is compressed air described in relation to safety?

A harmless by-product of engine operation

A backup to the service brake system only

A safe alternative to hydraulic fluid

A form of stored energy that can be hazardous

16 / 25

What type of product should be put into an alcohol evaporator?

Any type of alcohol

Windshield washer fluid

Engine coolant

Only products specifically designed for use in alcohol evaporators

17 / 25

Why must air tanks be drained regularly?

To increase fuel economy

To adjust the governor settings

To reduce brake fade

To prevent too much moisture and oil from collecting

18 / 25

What should you never do with any brake system component?

Read the manufacturer’s label on it

Dismantle, remove, repair or tamper with it

Check it during a pre-trip inspection

Inspect it visually

19 / 25

Why can compressed air in brake systems be hazardous?

It is poisonous to breathe in small amounts

It is too cold and can cause frostbite

It is highly flammable

It exits at high speed and can carry moisture, oil, dirt and dust

20 / 25

In what kind of climate is an alcohol evaporator especially important?

Tropical climates

Cold climates

Desert climates

Hot climates

21 / 25

When must a low air-pressure warning device activate at the latest?

Before pressure rises above 1035 kPa (150 psi)

Before pressure in either tank falls to 380 kPa (55 psi)

Before pressure reaches 552 kPa (80 psi)

Before pressure falls to 275 kPa (40 psi)

22 / 25

What does a safety valve venting air indicate?

The air dryer is full of moisture

The air tanks are low on air

There is too much pressure in the system and it needs immediate repair

The compressor is working normally

23 / 25

What is the role of safety valves in the air brake system?

To add alcohol vapour

To warn of low pressure

To remove moisture

To prevent over-pressure in the system

24 / 25

At approximately what pressure do safety valves normally open?

1035 kPa (150 psi)

690 kPa (100 psi)

345 kPa (50 psi)

552 kPa (80 psi)

25 / 25

Where is compressed air stored in a vehicle’s air brake system?

In the steering gearbox

In the fuel tank

In the supply (“wet”) tank and dual service (primary and secondary) air tanks

Only in the brake chambers

Your score is

This section tests knowledge of components like the compressor, governor, air dryer, and reservoirs, all of which are crucial for providing consistent air pressure for braking. Practice questions may cover how to identify problems, the importance of draining air tanks to remove moisture, and the function of safety valves. Mastering this chapter helps drivers prepare for the official test and ensures they can operate air brake systems safely and efficiently on Ontario roads.