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

To filter engine oil

To cool the compressed air for better performance

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

To increase system pressure above normal levels

2 / 25

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

A change in steering feel

A visual warning, such as a light

An engine shutdown

A vibration in the brake pedal

3 / 25

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

Increase engine speed to build pressure faster and continue driving

Pump the brakes repeatedly to test the system

Ignore it if the vehicle seems to brake normally

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

4 / 25

How is compressed air described in relation to safety?

A backup to the service brake system only

A form of stored energy that can be hazardous

A harmless by-product of engine operation

A safe alternative to hydraulic fluid

5 / 25

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

Any type of alcohol

Only products specifically designed for use in alcohol evaporators

Engine coolant

Windshield washer fluid

6 / 25

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

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

In the fuel tank

Only in the brake chambers

In the steering gearbox

7 / 25

What units of measurement may air pressure gauges display?

Volts and amps

Celsius and Fahrenheit

Litres and gallons

kPa and psi

8 / 25

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

To prevent over-pressure in the system

To warn of low pressure

To remove moisture

To add alcohol vapour

9 / 25

Why must air tanks be drained regularly?

To reduce brake fade

To prevent too much moisture and oil from collecting

To adjust the governor settings

To increase fuel economy

10 / 25

What do air pressure gauges in the cab indicate?

Air pressure in the primary and secondary air tanks

Pressure in the tires

Air temperature in the engine compartment

Pressure in the cooling system

11 / 25

What does a safety valve venting air indicate?

The air tanks are low on air

The air dryer is full of moisture

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

The compressor is working normally

12 / 25

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

To lubricate brake components

To cool the air compressor

To add alcohol vapour that mixes with moisture and reduces freezing

To increase overall air pressure

13 / 25

Why can compressed air in brake systems be hazardous?

It is highly flammable

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

It is poisonous to breathe in small amounts

It is too cold and can cause frostbite

14 / 25

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

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

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

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

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

15 / 25

What should you never do with any brake system component?

Check it during a pre-trip inspection

Read the manufacturer’s label on it

Dismantle, remove, repair or tamper with it

Inspect it visually

16 / 25

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

Cold climates

Tropical climates

Desert climates

Hot climates

17 / 25

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

Before pressure reaches 552 kPa (80 psi)

Before pressure falls to 275 kPa (40 psi)

Before pressure rises above 1035 kPa (150 psi)

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

18 / 25

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

To increase braking force

To prevent over-pressure of the system

To dry the air

To cool the compressor

19 / 25

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

A warning buzzer

Only one gauge with one needle

Two separate gauges or one gauge with two needles

Only a digital display

20 / 25

What is a wig wag in an air brake system?

A type of alcohol evaporator

A component of the air dryer

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

A type of safety valve

21 / 25

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

Yes, if the load is light

Yes, but only at low speeds

No, it is unsafe to drive in that condition

Yes, as long as the brakes feel normal

22 / 25

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

To help prevent moisture in the system from freezing

To reduce air tank volume

To increase brake application speed

To lubricate the compressor

23 / 25

At approximately what pressure do safety valves normally open?

1035 kPa (150 psi)

690 kPa (100 psi)

552 kPa (80 psi)

345 kPa (50 psi)

24 / 25

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

To measure coolant temperature

To monitor battery voltage

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

To display engine speed

25 / 25

Where might compressed air exhaust from an air brake system?

Only from the compressor intake

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

Only from the engine tailpipe

Only from the dashboard controls

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.