Why it’s hard to breathe in a respirator and how to change it

An adult person at rest makes an average of 14 breathing movements per minute. However, the respiratory rate may fluctuate considerably, from 10 to 18 per minute. During one breath at rest, 400-500 ml of air enters the lungs. This volume of air is called the respiratory volume. The same amount of air enters the atmosphere from the lungs during a calm exhalation. The maximum deep inhalation is about 2000 ml of air. The maximum exhalation is also about 2000 ml.

After maximal exhalation, about 1500 ml of air remains in the lungs, called residual lung volume. After a quiet exhalation, about 3000 ml remain in the lungs. This volume of air is called the functional residual lung volume.

Thanks to the functional residual lung volume, a relatively constant ratio of oxygen and carbon dioxide is maintained in the alveolar air, because the functional residual lung volume is 3-7 times greater than the respiratory volume. Only 60% of the respiratory volume reaches the alveoli of the lungs, which is called the alveolar ventilation volume.

An adult person with a respiratory volume of 0.5 liters and a rate of 14 breathing movements per minute lets 7 liters of air pass through the lungs per minute. Under physical activity, the breathing volume can reach 120 liters per minute.

When breathing is calm, the ratio of inspiration to exhalation in time is 1:1.3. Under intense activity and stress, the ratio of inspiration to exhalation changes to 1:0.9.

Without breathing, a person can usually live up to 5-7 minutes, after which there is loss of consciousness, irreversible changes in the brain and death. Breathing is one of the few abilities of the body that can be controlled consciously and unconsciously. With frequent and shallow breathing excitability of nerve centers increases, and with deep – on the contrary, decreases.

Types of breathing: deep and shallow, frequent and infrequent, the upper, middle (thoracic) and lower (abdominal). When physical activity prevails abdominal type of breathing. Special types of breathing movements are observed during hiccups and laughter.

Characteristics of breathing

1) Rhythmicity – the regularity of breaths and exhalations at regular intervals.

2) Frequency – the number of breaths per minute, 16 to 20 per minute in men and 18 to 22 per minute in women.

3) Depth – the volume of air in each breathing movement.

The Furtherium full face masks contain two chambers 0.43 liter volume with two replaceable filter tube-cartridges integrated into the mask housing. A fiberglass and synthetic fiber (PP, PS) pre-filter is installed on the top, which greatly saves the life of the main filters and increases the efficiency of the HEPA/ULPA filters by trapping larger particles in suspension (dust, aerosols) and liquids.

In the middle of the filter tube-cartridge, specially treated activated carbon pellets are used and a different type of oxidizer can be additionally used depending on the purpose of the filter (CO2, CO, certain organic gases and aerosols; certain inorganic gases and aerosols, SO2 and other acidic gases and aerosols, NH3 and derivatives of organic ammonia, mercury vapor).

Around the rod there are HEPA-14 or ULPA-15 filter folds that trap the remaining very small contaminant particles up to 5 nanometers (dust particles, bacteria, aerosols, viruses, gas molecules). The peculiarity of HEPA and ULPA filters operation is the simultaneous use of 4 filtration mechanisms: entrapment effect, diffusion effect, inertial collision effect and electrostatic attraction effect. These fine filters use the physics of atomic forces to trap molecules that are many times smaller than the distance between the filter fibers.

The filtering area of the two Furtherium HEPA and ULPA filters is 4055 cm2. When breathing calmly at a volume of 7 liters per minute and 14 breaths at a ratio of 1:1.3, the airflow rate through the filter is 1.73 cm/min or 0.07 cm/s. When breathing during an intensive and stressful period of 120 litres/minute and 80 breathing movements at a 1:0.9 ratio, the airflow through the filter is 29.59 cm/min or 0.94 cm/s. According to DIN EN 1822 the maximum permissible airflow rate for HEPA-13 is 5.3 cm/s, for HEPA-14 and ULPA-15 1.7 cm/s.

What this means in practice. The highest quality filtration process of 99.9995% (by the number of particles up to 60 nanometers per liter of air) provides only filters HEPA-14 and ULPA-15, which have a fiber diameter of up to 650 nanometers and the distance between the fibers of 0.3-40 micrometers. On the other hand, however, they offer the greatest resistance to airflow and require a significantly lower airflow rate. The larger the filter area, the lower the resistance to air pressure encountered during inhalation. Over time, the tiny particles trapped in the filter fibers become an integral part of their structure, and the efficiency of the filter increases. It is not necessary to change this filter more than once every few months. It is sufficient to replace the pre-filters and the filter core with an oxidant. Dry methods, including ozone, should be used for disinfection after use.

In comparison, one of the popular P3 HEPA cartridges 6035  from respirator and full-face mask manufacturer 3M has a calculated filtration area of 672 cm2. Two such cartridges in a respirator or full-face mask have a filtration area of 1344 cm2, 3(!) times less than our product. If breathing intensively at 120 liters per minute, the flow rate is 89.29 cm/min or 2.83 cm/s. Clearly, it is not possible to use higher quality HEPA-14 or ULPA-15 at these rates. However, these cartridges have become very popular, and we can confirm for ourselves that there is little difficulty in breathing in them. Nevertheless, these cartridges company 3M do not allow to filter other organic and inorganic pollution, and the combined cartridges 3M, protecting from certain organic and inorganic compounds, gases, vapors, dust and aerosols (AXP1-3, ABEK2P3) have an even smaller filtering area from small particles, respectively have a shorter life and more difficulty in breathing. This is understandable, because the manufacturer is interested in increasing sales of consumables such as filter cartridges, many of which are designed for 2-4 hours and no more than one 8-hour replacement.

There are situations where organic or inorganic compounds are highly toxic or their content in the air significantly exceeds the maximum allowable concentration for the possibility of effective filtration. Or in cases of fires where the oxygen content of the air is very low and the carbon monoxide content is very high. In these cases, it is necessary to use an air supply from a compressed air cylinder (SCBA – self-contained breathing apparatus) with a pressure reducer connected directly to the outside of one of the filters with a quick disconnect coupler. While the inlet of the second filter is blocked by turning 30°.

In extreme situations, when the supply of compressed air is exhausted and the person is still in the danger zone, the use of filters will help save his life.

It is also necessary to pay attention to the following. It is very often seen when firefighters are working in toxic smoke situations where they do not use SCBA to breathe when they have them on their backs, probably out of economy. Or the crew members don’t have them at the time: engineers, captains, paramedics. We know the sad stories of the dedicated firefighters who were on the front lines during the September 11, 2001 attacks. Most of them later developed cancer due to asbestos dust poisoning. The use of filters may have provided them with adequate protection.

The same goes for landscape hotspots. You almost never see anyone there using SCBA, which usually last about 45-80 minutes (5-9 liters). People in the area of wildfires receive large doses of carbon dioxide and carbon monoxide poisoning and other toxic carcinogenic compounds.

In our product composition we offer the best respiratory protection for professionals, which does not hinder breathing.

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