Difference Between Inhalation and Exhalation


An Introduction to Inhalation and Exhalation with Key Differences on Vedantu

Both inhalation and exhalation are two significant components of the respiratory system. The respiratory system is a cluster of organs that are involved in the exchange of oxygen and carbon dioxide within the body. These two processes strictly follow Boyle’s Law that states pressure and volume are inversely proportional; likewise, these two parts of respiration rely on the pressure between the lungs and atmosphere. Along with that thoracic cavity plays a significant role in breathing.

However, the inhalation and exhalation processes are different from each other. Nonetheless, both of them are dependent on each other in completing a full circle of respiration.

It is only through inhalation and exhalation that your body brings in oxygen and expels carbon dioxide. This process is facilitated by a large dome-shaped muscle under your lungs called the diaphragm.


A healthy adult takes typically 12-18 breaths per minute. While an inhalation takes two seconds, an exhalation requires three seconds on average.

Meaning of Inhalation

Inhalation definition refers to the process of breathing in air, containing oxygen and transporting it to the lungs. It is the first segment of respiration and is known as an active process. During inhalation, the diaphragm and intercostal muscle contract, which results in the expansion of lung volume. Simultaneously, the thoracic cavity expands, creating a difference in pressure between the atmosphere and the alveolus and allowing air to enter the lungs.

It is an autonomic process that does not require any conscious control or effort but can be (within limits) consciously controlled or interrupted.

Once you get an idea of what inhalation is now, it’s time to learn about exhalation.

Meaning of Exhalation

Similarly, exhalation is the process of releasing air containing carbon dioxide out of the lungs. It is the concluding part of respiration and is referred to as passive action. During exhalation, the diaphragm relaxes and moves towards the thoracic cavity. This occurs due to the elastic properties of the lungs and the internal intercostal muscles, which lowers the ribcage and decreases thoracic volume. In this process, the pressure within the thoracic cavity increases and allows the airflow out of the lungs.

When forced exhalation occurs (ex-blowing out a candle), expiratory muscles, such as the abdominal and internal intercostal muscles, produce abdominal and thoracic pressure, forcing air out of the lungs.

The inhalation and exhalation processes are spontaneous events that do not require any conscious effort.

However, just like inhalation can be controlled within limits, we can also break down the conscious control of your exhalation into two categories of, voluntary control and involuntary control.

Air is held in the lungs and slowly released at a fixed rate during voluntary exhalation.

Ex - singing, playing an instrument, exercising.

Dissimilarities Between Inhalation and Exhalation

Point of Difference




Drawing air and other gases into lungs.

Expelling carbon dioxide from the lungs. 


As muscles contract during the process, it is an active event.

As muscles do not actively contract, it is a passive event.

Chest Size



Role of Diaphragm

Moves lower due to contraction. 

Moves back higher due to relaxation and takes up the shape of a dome. 

Lung Volume

Increases and inflates.

Decreases and deflates.

Intercostal Muscle Function


Internal muscles relax and external muscles contract.

Internal muscles contract and external muscles relax.

Intercostal Muscle Effect 

Ribcage moves forward and upward.

Ribcage moves backwards and downward. 

Components of Air

A Mixture of oxygen and other gases is inhaled.

A Mixture of carbon dioxide and nitrogen is exhaled.

Air Pressure




Transporting oxygen to blood cells through lungs.

Expelling carbon dioxide from the body via lungs. 

The following table contains the striking differences between the inhalation and exhalation processes.

Mechanism of Inhalation and Exhalation

The lung is the primary organ that actively takes part in respiration. However, several other supporting muscles and organs aid in carrying out the inhalation and exhalation process.

  • Both Inhalation and Exhalation occur due to Pressure Gradients. 

  • During Inhalation, the lung volume increases. According to Boyle’s law, lung pressure reduces compared to atmospheric pressure. It makes the air rush into lungs. Afterwards, blood promptly transports the air containing oxygen to every part of the body. 

  • The process of inhalation starts when we inhale air through our nose or our mouth. From there, it travels down through your windpipe which is divided into airways called bronchial tubes. These airways always need to be open and free of any inflammation or mucus for our lungs to perform their best. 

  • The air flows through bronchial tubes into our lungs, dividing into several smaller airways called bronchioles. These bronchioles divide into even smaller balloon-like structures called alveoli. Our body contains about 600 million alveoli. 

  • Tiny blood vessels, called capillaries, form a mesh around the alveoli. It is at this stage that the oxygen that was previously inhaled is filtered and passed into your blood. 

  • After absorbing the oxygen, the blood then goes to our heart. The heart pumps the blood all through our body to the cells and organs.

  • The cells and organs absorb the oxygen, producing carbon dioxide which goes back into the blood. 

  • In the case of expiration, the lung volume decreases because of the elastic flinch of lung tissues. As a result, the pressure within the lungs increases compared to the outside pressure. It allows the air carrying carbon dioxide to push out of the body. 

  • Diffusion in the alveoli allows for the exchange of O2 into the pulmonary capillaries as well as the removal of CO2 and other gases to be exhaled. The diaphragm relaxes for the lungs to release air, pushing up on the lungs. The air then passes via the trachea, larynx, and pharynx before exiting the body through the nasal cavity and mouth cavity.

  • The tiny sacs within the lungs or alveoli also play a crucial role in respiration. 

  • During inspiration, alveoli help in exchanging oxygen with bloodstreams. On the other hand, during expiration, take out carbon dioxide from the blood.

Fill in the Gap: Aerobic respiratory passage is also known as ____________ pathway.

Answer: Amphibolic 

Gaseous Components During Inspiration and Expiration


Percentage of Inhaled 

Percentage of Exhaled





Oxygen helps in retaining the cellular activity of an organism.

Carbon dioxide



Carbon dioxide comes out as a waste product of the breathing process. 




Nitrogen gas does not take part in cellular activities.



On higher side

During exhalation, a little amount of water evaporates and gets mixed in the air. 

Did You Know?

  • The Tennis court and lung size can be the same! It may seem absurd, but if the lungs are cut open, it can cover an entire tennis court!

  • The lungs can float on water. It is the only human organ that is capable of doing so.

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FAQs (Frequently Asked Questions)

1. Which one takes more Time, Inhalation or Exhalation?

Exhalation consumes more time than inhalation. The air we exhale contains not only carbon dioxide but a mixture of other gases. Furthermore, inhalation is an active process, using the muscles in our diaphragm and our intercostal muscles. Exhalation, however, occurs passively as a result of tissue recoil, conserving the body’s energy for inhalation which occurs due to muscle contraction, making inhalation a more efficient process. The airways are also slightly narrowed during exhalation, compared to inhalation. Moreover, exhalation facilitates the exchange of gases better; thus, it requires more time.

2. Why is exhaled air hotter than inhaled?

Exhaled air is warmer than inhaled because our body temperature is higher than the surrounding temperature. The air we inhale travels down to our lungs, through our nose and the back of our throat. It is warmed when it comes in contact with the cells and tissues in our organs. It is also in contact with the same tissues when we exhale it back out. The air we exhale has been warmed by our body during both inhalation and exhalation and is, therefore, warmed by our body and hotter than the air we inhaled originally. Also, it contains the maximum amount of carbon dioxide. However, both the inhalation and exhalation process take part in gaseous exchange through alveoli.

3. How much carbon dioxide do we exhale per day?

Per day we exhale approximately 500 litres of carbon dioxide. It almost amounts to about 1 kg in mass. However, this amount heavily depends on someone’s activity level. To know more about this and more, visit the Vedantu app or website and access all our free study materials and guides.

4. What is the 4-7- 8 pattern while breathing?

It refers to a particular breathing sequence. Inhale quietly through the nose for 4 seconds. Then hold your breath for 7 seconds and finally breathe out forcibly through the mouth for 8 seconds. Repeating this process four times will improve the breathing flow. It requires a person to focus on taking long, deep breaths. This breathing pattern helps reduce anxiety, improve sleeping patterns, manage cravings, and control anger responses. Although the evidence of its effectiveness is limited to anecdotal reports from users and there is limited clinical research to support these claims.

5. What happens to the body during inhalation and exhalation?

The diaphragm and intercostal muscles contract during inhalation, causing the lung volume to expand and the thoracic cavity to enlarge. According to Boyle’s law, pressure is reduced as volume is increased and thus, air rushes into the lungs due to the pressure difference between the atmosphere and the lungs; inhalation occurs. Exhalation causes the lungs to recoil, forcing the air out of the lungs. The chest wall returns to its former place as the intercostal muscles relax. This causes the diaphragm to relax and move higher up the chest cavity. This raises the pressure within the thoracic cavity in comparison to the surrounding air. The pressure difference between the thoracic cavity and the atmosphere causes air to rush out of the lungs.