Translation:Proper use of gas masks as prevention of occupational diseases

Proper use of gas masks as prevention of occupational diseases

The Federal state unitary enterprise all-Russian research Institute of railway hygiene (CPS), 125438, Moscow

Abstract ''In the paper there are considered the problems arising from the use of respirators: 1. Modern methods used to replace the gas mask filter; 2. Conditions for safe re-use filters, that are not fully developed their service life period; 3. The conditions of safe use of respiratory protective equipment (RPE) in the immediately dangerous air pollution. Measures for protection of health, based on common practice of using RPE in the developed countries, which include: the development and application of regulations governing the selection and the use of respirators, filter replacement, training of staff have been proposed.''

Key words: respirator, RPE, gas mask filter, Immediately Dangerous to Life or Health (IDLH)

Different methods can be used to reduce the concentration of pollutants in the air of working area : sealing equipment, ventilation, etc., When this is not sufficient for safeguarding the health of workers, employees must use a respirator.

When using filter gas masks, employee inhales polluted ambient air after it is cleaned by gas filters (cartridges or canisters). This often uses cartridges filled with sorbent that absorbs harmful gases as the contaminated air passes through the cartridges. After saturation of the sorbent he loses the ability to absorb harmful gases, and they move further to the fresh non-saturated layers of the sorbent. When the sorbent was saturated enough, the contaminated air passes through the sorbent together with harmful substances, and harmful gases fall under the mask. Thus, the service life of the cartridges is limited. It depends on the concentration and properties of gases, the sorption capacity of the filter and its usage conditions (air flow, humidity, temperature), as well as proper storage. If the gas filter is not replaced in a timely manner, the impact of harmful gases per worker exceeds the maximum allowable, which may cause damage to health.

The degree of respirator’s protection is influenced by many different factors, so for reliable protection of the workers’ health in the developed countries, the use of respirators is happening in the context of a comprehensive respiratory protection program. They have been developed and applied regulations governing the selection and organization of the use of respirators: USA [9], Australia [5]., etc., and tutorials [7,8]. They require the employer to replace the gas filter in a timely manner, for which it is proposed:

1. The industrial hygiene specialist uses the results of measurement of air pollution, information about the conditions of work and information about the properties of the cartridges, and then they makes the schedule for cartridges replacement [13]. To do this, the manufacturers provide information about cartridges, or even free software, such as: MSA - http://webapps.msanet.com/responseguide/ChemicalCalculator.aspx, 3M - http://csrv.3m.com/csrv, Sperian - http://www.honeywellsafety.com/Products/Sperian/Respiratory_Protection/Respiratory_Training_Tools.aspx?site=/americas.

The user can also use a table with information about the service life of cartridges, designed for the particular conditions of use. This allows it to determine the lifespan with an error that depends on the accuracy of the source data, and change the cartridges in a timely manner.

2. With increasing saturation of the sorbent, the concentration of harmful gases at the outlet of the cartridges gradually increases. This allowed to develop indicators of end-of-service-life of cartridges (ESLI), triggered earlier than the concentration at the outlet of the cartridges reaches the maximum allowed. Developed requirements for such indicators, ensuring their safe use. While compliance with these requirements by the manufacturers of respirators allows workers to change filters in a timely manner and to use the respirator without risking their health (e.g. cartridges 3M 6009 60929 with an ESLI indicator, that changes its color).

3. Inhalation of harmful gases can lead to reactions of the senses of the employee (smell, taste, irritation etc.). Studies have shown that this reaction depends on various factors (gas composition, concentration, individual susceptibility, employee health, conditions of work and how quickly increases the concentration of gases, and whether the person knows the smell). It turned out that people have different thresholds for perception of the smell of one substance. For 95% of people, it is between the upper and lower limits that differ from the “average” value of 16 times (higher or lower side). This means that 15% of people do not smell at a concentration 4 times greater than the sensitivity threshold. This has also resulted in different sources may have different values of the threshold of perception of smell. One’s perception is influenced by the condition - cold can reduce the sensitivity. If the concentration will increase gradually (as occurs when the saturation of the sorbent), then the worker can be “addictive”, and the response to the seepage of gases will occur at concentrations significantly exceeding their concentration with a sharp increase. If the job requires more attention, it also reduces the threshold of perception of smell [8].

Therefore, the worker can begin to respond to inhalation of harmful gases at various concentrations. Is it possible to use this reaction for cartridges replacement?

There are harmful gases that have no taste or smell at concentrations exceeding the Permissible Exposure Level (PEL) (e.g. carbon monoxide). In this case, this method of cartridges replacement is unacceptable. There are gases that have “average” threshold of perception is significantly higher than the PEL. Below is a list of some of these substances with their concentrations in which people (on average) are beginning to smell. Concentration is expressed in PEL. The PEL values and the average threshold of perception is taken from [10], and may not correspond with the values that would be when using information from Russian sources.

҂ - Time-weighted average PEL are in: ppm (mg/m3), where ppm - parts per million ppm,

† - Average concentration (PEL), in which people begin to feel the smell.

When working with these substances, You cannot use the response of worker inhalation of harmful substances - many workers will smell too late.

But there are substances in which the average threshold of perception of a smell below the PEL. Is it possible in this case to use the reaction working on it for timely replacement of cartridges?

In 1987 in the USA, this was allowed [7]. But it is required before the employee is to commence work, the employer checked the individual threshold of perception of odors this work, giving him a whiff of harmful gas at safe concentrations. If harmful gases had no "warning properties" (odor, irritation, etc.) the use of filtering respirators were forbidden.

In 2004 the opinions of experts has changed [8]. Use the reaction of workers to the inhalation of harmful substances for the timely replacement of cartridges is not recommended, and replacement gas cartridges according to the reaction worker inhalation of harmful substances is not allowed.

As exposure to harmful substances under the mask can occur not only through the cartridges, but also through the gaps between the mask and the face (for example, due to slipping of the mask during work, etc.), then the reaction is working on inhalation of harmful substances will allow time to notice the danger and to leave the dangerous place.

In cases when the use of the cartridges is stopped earlier than the concentration of harmful gases at the outlet of the cartridges has reached the maximum allowable, the cartridges remains unspent sorbent. This can occur when using the cartridges in a short time interval or in low air pollution. The study [11] and others showed that during storage of the such cartridges, the harmful gases (captured earlier by the sorbent) can be freed, and the concentration of gases inside the filter at the inlet will rise. In the middle of the cartridges and at the outlet of the cartridges will be the same - but to a lesser extent (due to a lower saturation of the sorbent). Because of the differences in gas concentrations, the molecules begin to move inside the filter from inlet to outlet, redistributing harmful substance inside the cartridges. This process depends on various parameters - “volatility” hazardous substances, storage duration and conditions of storage, etc. This can lead to the fact that when one reuse such (not fully expended) cartridges, concentration of harmful substances in the air which has passed through it, will be above the maximum permissible immediately. Therefore, the standards of the Russian Federation [2,4] be obliged to apply the cartridges “for single use only", but this indication is not supported by legislation, guidance manuals and violates the long time practice of using civilian gas masks.

Currently, according to the standards [1-4] "volatile" are considered to be substances with a boiling point below 65°C. But studies have shown that at the boiling point >65°C reuse of the gas cartridges can be unsafe. In the paper [12] gives a procedure for calculating the concentration of harmful substances at the start of the re-use of cartridges, but these results are not yet reflected no standards or guidelines on the use of respirators, compiled by the manufacturers (where the repeated use of such gas filters is prohibited). It is interesting to note that the author has not attempted to consider using gas cartridges more than two times.

The harmful gases beneath the mask can cause not only chronic diseases. Even short-term inhalation of harmful substances at sufficiently high concentrations can cause death or permanent damage to health, and effects on the eyes can prevent to leave the dangerous place. When gas cartridges are replaced in a timely manner, this may happen when there are gaps between the mask and the face. Then one inhaled the air, the pressure under the mask became below atmospheric pressure. Studies have been conducted to measure the protective properties of respirators in the laboratory and in the workplace. They showed that in practice the degree of protection is a random variable (even for one business, use the same respirator and perform identical movements), and that during operation of respirators without positive pressure under the mask the degree of protection may be reduced to very small values - see figure [6].



Therefore, the occupational hygiene and safety standards of developed countries, that govern the selection and organization of the use of respirators, requiring employers to provide workers with respirators with forced air supply under the mask to create excess pressure during inhalation to prevent leakage. To do this, people use an independent source of air (or clean air supplying through the hose - if such mobility restriction is permissible). In the latter case, for the safe evacuation of employees from the workplace (for example, at the termination of the air through the hose), they should have an independent source of clean air of sufficient capacity to evacuate [9].

At very high concentrations of harmful substances in the air use of filtering respirators are not recommended - even if the concentration of harmful substances is not instantaneous danger to life and health. In addition, the use of filter masks in such conditions may require too frequent replacement of cartridges, which are expensive. In such cases it may be more advantageous to use respirators to supply clean air under pressure through the hose.

Respirators may not provide a high degree of protection - always and continuously. Therefore, and because of the "human factor", the US and EU occupational health and safety standards (and Sanitary Rules СП 2.2.2.1327-2003 in RF) require the use of any other ways to reduce the harmful effects (ventilation, etc.) even when they do not manage to reduce polluted air to the PEL.

Practice has shown that the correct choice of appropriate respirators good quality, their individual selection, and proper and timely application by trained employees (within a comprehensive respiratory protection program) - the likelihood of damage to health becomes very low.

Conclusion

For various reasons, industrial hygienists are not well taught the proper selection and use of respiratory protective equipment in the USSR and in the RF. There are no official documents in RF, that would determine when any respirators can be used, and indicates how to use them. No specific requirements for the replacement of gas cartridges, use a respirator with a constant pressure under the mask, there is no requirement for training workers. The absence of these requirements prevents develop training manuals, and constrains the application of modern western development. Lack of training of occupational health and safety inspectors may reduce the effectiveness of their checks to zero.

Improper use of RPE can lead to occupational diseases, which often remain undetected in the RF. As a result, the employer loses skilled personnel, workers lose motivation, and society is faced with demographic problems. Unavoidable (due to lack of training) errors in the selection and use of respiratory protective equipment undermine the faith of potential buyers in the effectiveness of respirators. For this reason, sometimes the workers did not use respirators issued to them, and the employer does not buy RPD when required. This helps reduce the productivity of labor (because of the "time to protect" - obviously or hidden), the reduction of the gross of domestic product, and most importantly - leads to increased morbidity and mortality in the working age.

There is a need to develop normative documents on the selection and use of respiratory protective equipment organizations in RF, increase the responsibility of the manufacturer's RPD and the employer for personal injury, and to stop the substitution of science-based measures to protect the health of workers by palliative measures.

References
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