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Aparat cu aductiune de aer comprimat ariac ariacaparat evacuare escape

Short Technical Manual for
Respiratory Protection


Respiratory protective devices can be considered as a constituent part of the respiratory system, so that the analysis of the protection must take into account both its mechanism and physiological factors. Breathing is a complex physiological process which involves three different functional systems: the respiratory system, the cardiovascular system and the nervous system. The respiratory system consists mainly of the lungs and extrapulmonary airways.

Inhalation and exhalation represents active or passive, respectively, breathing. These two processes generate pulmonary ventilation. At rest, during normal breathing, respiratory movements occur with a frequency of 16 to 18 strokes per minute. The volume of air circulated in a normal breathing session, called current air or respiratory air ranges, from 0.4 to 0.6 liters, but the amount of air forced inhaled may be up to 1.8 liters.

The amount of air passing through the lungs in one minute is the respiratory flow, which at rest has the value of 5-10 liters/minute, but which during an exercise can reach values ​​between 120 and 150 liters/minute. Let us not forget that there are great differences in terms of how various people adapt to effort, an important role being borne by training and stress.

The amount of air passing through the lungs in one minute is the respiratory flow, which at rest has the value of 5-10 liters/minute, but which during an exercise can reach values ​​between 120 and 150 liters/minute. Let us not forget that there are great differences in terms of how various people adapt to effort, an important role being borne by training and stress.


Breathing is a complex physiological process whose dysfunction can cause serious or even fatal accidents. In this context, people’s entering toxic or low-oxygen environments is particularly dangerous, if it is done without proper protection.

Atmospheric air has the following normal composition:


When conducting various activities, workspaces’ pollutants acting on the respiratory tract vary widely, ranging from relatively harmless but “annoying” agents to very dangerous agents that generate serious poisoning, being driven by a number of factors relating to the amount and concentration of the active substance, the cumulative action in the body, the exposure time, the temperature of the working environment, physiological features.

The main pollutants encountered can be classified into three distinct categories:

The last category of harmful air can result indoors in slow burning or oxidation of organic materials and massive discharge of other gases (CO2, N2, inergen extinguishing agents, and so on). In such conditions, oxygen depletion is followed by the addition of toxic gases (oxide and carbon dioxide) resulting from combustion.


Under certain conditions, a person can live in an atmosphere containing less oxygen than normal, as follows:

It is important to note that a human being cannot detect the decrease in oxygen concentration, because breathing is not regulated by oxygen, but by carbon dioxide, which is an excitant for the respiratory nervous center.


In general, a person can tolerate just fine a concentration of up to 4% carbon dioxide in the air to breathe.

Breathing in the presence of chemical compounds (which can result also from burning) such as cyanides, ammonia, hydrogen sulfide and more, even in relatively small percentages, can cause severe poisoning or even death.


Two types of respiratory protection devices can be used for respiratory protection, also called respiratory protection devices (RPD):


Breathing apparatus (insulating, self-contained) are used in the following situations:

Using breathing apparatus under critical conditions is therefore a vital necessity. Because intervention in a hostile environment is stressful, the apparatus’ user needs to have full confidence in the equipment so his/her attention can be focused mainly on the work to be performed. This trust is given by structural characteristics and reliability. Also the user must be in a very good physical and mental condition and must train with the breathing apparatus as air consumption is dependent on lung capacity, but also on training and the level of effort.


For the theoretical calculation of the duration of use of the self-contained breathing apparatus by a person during work, the following formula can be applied:

T = (p - t) V /C

where:

T – is the length of the remaining time until the whole air supply is consumed
p – existing average pressure in the air cylinder at a given time (e.g., 200 bars)
t – spare pressure (e.g., 55 bars)
V – total volume of cylinders (e.g.: 4 liters x 2 = 8 liters)
C - air consumption in liters per minute necessary for breathing and appropriate for the effort category.

The functional autonomy of breathing apparatus varies depending on air consumption, in liters per minute. Thus, for different activities, as a rough guide, air consumption in the following table can be considered:

 

Nature of the position or effort

breath/min.

Volume of one breath [liters]

Air consumption

[liters/min.]

Laying down

14

0,35

4,9

Siting

18

0,40

7,2

Marching, 85 steps/min.

20

0,75

15,0

Marching, 125 steps/min.

23

1,4

32,0

Running, 165 steps/min. or climbing a 111 steps ladder in 80 seconds

24

1,7

40,8

Running 220 steps/min.

40

2,0

80,0

Running on a 111 steps ladder in 28 sec.

40

2,6

104,0

Values ​​can be influenced considerably by the physiological peculiarities of the subject, his/her training and mental state.


Performance of respiratory protective devices can be expressed in terms of harmful substance concentration inside the facepiece cavity (C1) and harmful substance concentration outside the facepiece (C0).

The relationship between C1 and C0 can be expressed as penetration factor (C1/C0), efficiency factor (C0 - C1)/C0 or protection factor (C0/C1). The protection factor is determined by the relationship between penetration (p%) and efficiency (E%) as follows:

Protection factor = C0/C1 = 100/p(%) = 100/100-e(%)

In general, the term C1 of the protection factor takes into account the total run inside the facepiece. When examining different sources of flight inside the apparatus or different techniques are used to determine both C0 and C1, the resulted report’s expressions show distinct descriptions, such as tightness factor or laboratory protective factor. All performance measurements using the ratio of the concentrations inside and outside the facepiece are based on the above equation, the difference being the limits and conditions imposed to concentration measurements, especially C1.