Anatomy of the Lungs and How to Breathe Safely
A basic review of the anatomy, physiology and personal protective equipment related to the respiratory system.
- By Jeff Buckau
- Jun 30, 2025
On average, we breath around 20 times per minute, every minute and every hour, day, week, month and year of our lives. It is one of the first things we do immediately after birth and one of the last things we do at the end of our lives.
We can go for three days without water and about three weeks without food. But longer than three minutes without oxygen and our body’s systems and organs start to have significant issues. The brain cannot continue to function normally if it does not get air. Yet, we do not consciously think about breathing until that bodily function is jeopardized.
How It all Works
The basic anatomy of the human body consists of the air passage channels of the head and neck. The nasal passage is called the nasopharynx, and the oral passage is called the oropharynx. Both connect in the back of the throat and superior to the opening of the trachea which is blocked during the swallowing of food or beverage by the epiglottis. The epiglottis helps keep items that are supposed to go to the stomach from going down the “wrong pipe,” the trachea. The trachea divides into two branches called the right and left main bronchus.
The bronchial tubes then enter the lungs with three lobes in the right lung and two lobes in the left. Once into the lobes of the lung the bronchioles continue to divide down the microscopic level of the alveolar systems. Picture a bunch of grapes on a vine, which is how the alveoli appear. In each alveolus, they continue to divide until the individual alveoli encounters the circulatory system, the microscopic capillary system. The alveoli/capillary system is separated by a permeable membrane that allows the CO2 and O2 to pass between. The capillary is carrying deoxygenated blood from the heart and discharges its cargo of CO2 into the alveoli and admits the O2 from the alveoli into the blood stream.
From there the oxygenated blood returns to the heart into the left atrium and then into the left ventricle where is it pumped through the aorta to all systems of the body. The O2 is then used to allow the cellular structures to breathe, a process called cellular respiration (a completely separate and very in-depth study). (Buckley, 2021).
The CO2 is carried out of the alveoli and back through the respiratory system where it is blown off during exhalation. The air that we breathe in our atmosphere contains approximately 21.5 percent oxygen plus or minus 2 percent. There are other components to the atmosphere but for this discussion we will be focusing on the oxygen.
For example, COVID-19 attacked and destroyed the connection between the alveoli and capillary and would not allow the gas exchange to occur (Yu, 2023). Many people became extremely ill with life-threatening conditions to the point of being placed on ventilators.
There are many ways for the respiratory system to be damaged. This can be an acute process or something more sinister and chronic. Smoke inhalation from fires is one such example. Carbon monoxide (CO) is also an example. Inhaling certain toxic chemicals like the smoke from welding on or heating up of stainless steel or other metals containing chromium (OSHA, 2025).
We monitor confined spaces and excavations using four gas monitors. One of the areas of monitoring is oxygen (O2) concentrations and another is CO monitoring. CO has an affinity for hemoglobin that is far greater than the affinity for O2 (Palmeri, 2023). That means that CO binds to the hemoglobin faster than O2. The hemoglobin molecule in the blood is the transport medium for O2 to the cells for the previously mentioned cellular respiration process. If the hemoglobin is busy with CO, then O2 will not be transported, and the cells will begin the process of suffocation. This is why monitoring for CO and O2 concentrations is so important in excavations and confined spaces.
Another area of concern is the actual damage to the lung tissue caused by the inhaled toxins such as smoke, dust, silica, asbestos, pollen and other items.
Damaging the Lung Tissue
Diseases such as chronic obstructive pulmonary disease (COPD) and Idiopathic pulmonary fibrosis (IPF) are processes that damage the lung tissue on the gross anatomy level. Silicosis and asbestosis are also disease processes that damage lung tissue. Some toxins inhaled can lead to lung cancer and other types of cancer.
So how do we protect people from things that can damage or destroy the respiratory system? If we implement the hierarchy of controls using the inverted pyramid, we find that elimination is our first and best option.
If the person is not exposed to the toxin in the first place, then the worry for the employee being injured is far less. Going back to the COVID-19 issue, we eliminate the exposure by keeping our distance from others. As the virus was mostly respiratory droplets spread and the droplets were far heavier than air, and usually fell to the ground in about three to four feet, so if we maintained a distance of 6 feet, we had a far less chance of becoming ill
Substitution is also one of the better options for controls. Using the Safety Data Sheets (SDS) for chemicals, one could read that certain compounds contained a higher level of contaminates than others. Consider the cleaning solutions of bleach and ammonia. Changing out one or both of those compounds reduced the life-threatening problems associated with combining them together.
Engineering out the toxin is another way to separate the individual from the hazard. Administratively controlling is still more effective than relying on the personal protective equipment (PPE). We know that PPE is the least effective and last line of defense. The usual PPE for respiratory issues is the barrier method. Cloth mouth and nose coverings, N95 masks, filtered masks, respirators that are both air supplied artificially and naturally, self-contained breathing apparatus, negative and positive pressure environments, etc. Each of these provide some form of protection to the wearer, but depending on the size of the toxin, the barrier might not be of much benefit.
So, the key to the respiratory system insult and preventing the damage caused by the toxin lies with the knowledge of the chemical that the employee/worker has. And that information is found in the SDS system that should be available to all employees through their company’s hazardous communication system.
One last item to consider is: What is the employee doing voluntarily that might make the exposure to another offending item more serious? For example, smoking tobacco products and silica exposure (Tse, et al, 2014). Silica exposure is of great concern to OSHA, however, adding in tobacco use in the form of inhaled smoking materials makes the silica issue far worse down the road. It is difficult to get employees to follow the hierarchy of controls for safety management systems much less have them make lifestyle changes to avoid long term and chronic illness consequences.
In conclusion, considering the physiology of the human body and the use of the hierarchy of controls for safety management, the safety professional will be well-armed to help prevent and ultimately eliminate the life-altering effects of respiratory system insult to the employees we are dedicated to helping.
REFERENCES:
- Lim ZJ, Subramaniam A, Ponnapa Reddy M, Blecher G, Kadam U, Afroz A, Billah B, Ashwin S, Kubicki M, Bilotta F, Curtis JR, Rubulotta F. (2021). Case Fatality Rates for Patients with COVID-19 Requiring Invasive Mechanical Ventilation. A Meta-analysis. Am J Respir Crit Care Med. 2021 Jan 1;203(1):54-66. doi: 10.1164/rccm.202006-2405OC. PMID: 33119402; PMCID: PMC7781141.
- OSHA, (2025). Hexavalent Chromium. As retrieved from the Occupational Safety and Health Administration website, https://tinyurl.com/ycywenc3.
- Palmeri R, Gupta V. (2023). Carboxyhemoglobin Toxicity. [Updated 2023 Apr 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://tinyurl.com/mryyeefn.
- Toufen Junior C, Pêgo-Fernandes PM. (2021). COVID-19: long-term respiratory consequences. Sao Paulo Med J. 2021 Aug-Sep;139(5):421-423. doi: 10.1590/1516-3180.2021.139526052021. PMID: 34287513; PMCID: PMC9632533.
- Tse LA, Yu IT, Qiu H, Leung CC. (2014). Joint effects of smoking and silicosis on diseases to the lungs. PLoS One. 2014 Aug 8;9(8):e104494. doi:
- 10.1371/journal.pone.0104494. PMID: 25105409; PMCID: PMC4126694.
This article originally appeared in the June 2025 issue of Occupational Health & Safety.