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

Why must air tanks be drained regularly?

To prevent too much moisture and oil from collecting

To reduce brake fade

To increase fuel economy

To adjust the governor settings

2 / 25

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

To lubricate brake components

To add alcohol vapour that mixes with moisture and reduces freezing

To increase overall air pressure

To cool the air compressor

3 / 25

What should you never do with any brake system component?

Check it during a pre-trip inspection

Dismantle, remove, repair or tamper with it

Inspect it visually

Read the manufacturer’s label on it

4 / 25

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

Pump the brakes repeatedly to test the system

Increase engine speed to build pressure faster and continue driving

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

5 / 25

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

To remove moisture

To warn of low pressure

To add alcohol vapour

To prevent over-pressure in the system

6 / 25

Why can compressed air in brake systems be hazardous?

It is too cold and can cause frostbite

It is highly flammable

It is poisonous to breathe in small amounts

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

7 / 25

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

To reduce air tank volume

To help prevent moisture in the system from freezing

To increase brake application speed

To lubricate the compressor

8 / 25

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

Windshield washer fluid

Only products specifically designed for use in alcohol evaporators

Any type of alcohol

Engine coolant

9 / 25

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

To increase braking force

To dry the air

To prevent over-pressure of the system

To cool the compressor

10 / 25

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

Two separate gauges or one gauge with two needles

Only one gauge with one needle

Only a digital display

A warning buzzer

11 / 25

Where might compressed air exhaust from an air brake system?

Only from the engine tailpipe

Only from the compressor intake

Only from the dashboard controls

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

12 / 25

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

A change in steering feel

An engine shutdown

A visual warning, such as a light

A vibration in the brake pedal

13 / 25

What does a safety valve venting air indicate?

The air tanks are low on air

The compressor is working normally

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

The air dryer is full of moisture

14 / 25

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

Yes, but only at low speeds

Yes, if the load is light

No, it is unsafe to drive in that condition

Yes, as long as the brakes feel normal

15 / 25

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

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)

Before pressure rises above 1035 kPa (150 psi)

16 / 25

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

Hot climates

Tropical climates

Desert climates

Cold climates

17 / 25

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

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

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

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

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

18 / 25

What is a wig wag in an air brake system?

A type of safety valve

A component of the air dryer

A type of alcohol evaporator

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

19 / 25

What do air pressure gauges in the cab indicate?

Pressure in the cooling system

Air temperature in the engine compartment

Pressure in the tires

Air pressure in the primary and secondary air tanks

20 / 25

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

Only in the brake chambers

In the fuel tank

In the steering gearbox

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

21 / 25

What units of measurement may air pressure gauges display?

Volts and amps

Litres and gallons

kPa and psi

Celsius and Fahrenheit

22 / 25

At approximately what pressure do safety valves normally open?

345 kPa (50 psi)

552 kPa (80 psi)

1035 kPa (150 psi)

690 kPa (100 psi)

23 / 25

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

To display engine speed

To monitor battery voltage

To measure coolant temperature

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

24 / 25

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

To increase system pressure above normal levels

To cool the compressed air for better performance

To filter engine oil

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

25 / 25

How is compressed air described in relation to safety?

A harmless by-product of engine operation

A form of stored energy that can be hazardous

A backup to the service brake system only

A safe alternative to hydraulic fluid

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.