Iii. basic operations and calculations for the analysis of the dustiness of the working room. Determination of dust concentration in the air Methods for normalizing the air composition of the working area

Federal Agency for Sea and River Transport

Federal State Budgetary Educational Institution

Higher professional education

"STATE MARITIME UNIVERSITY NAMED AFTER ADMIRAL F.F. USHAKOVA "

Department of "Life Safety"

Practical work № 3

on the topic of:

"Determination of the class of working conditions by factor

"ASSESSMENT OF HARMFUL EXPOSURE TO DUSTS"

Cadet group 1922

Somkhishvili Irma

Checked by: Senior Lecturer

Pisarenko G.P.

Option 22

I. PURPOSE OF THE WORK

To study the general properties of industrial dust and the requirements of sanitary standards; familiarization with the device and operation of the aspirator; determine the content of dust in the air by the gravimetric method and give a sanitary assessment of dust content.

II. GENERAL INFORMATION ON INDUSTRIAL DUST

Industrial dust refers to particulate matter suspended in the air, i.e. these are dispersed systems, namely aerosols, where the dispersed phase is particles with a size from 10 -2 to 100 microns, and the dispersed medium is air.

Industrial dust is formed during reloading and transportation of bulk cargo, mechanical crushing of solids.

Industrial dust can also include soot formed as a result of incomplete combustion of fuel in marine diesel engines and steam generators.

Industrial dust can be quantitatively characterized by the average particle size, size distribution curve, specific surface area, i.e. the ratio of the total surface of dust particles to their mass or volume. The most important characteristic is the concentration of dust in the air.

Dust enters the human body through the respiratory system, gastrointestinal tract, eyes and skin. For humans, the greatest danger is represented by dust particles less than 10 microns in size, which can be seen from the data given in Table 1

Table 1

Particular danger for the human body is dust, consisting of particles of a toxic substance, or dust that has sorbed toxic substances... For example, dust of coal sand, calcium carbide, lime, lead, etc. is considered toxic. A special feature is the presence of adsorbed carcinogenic substances on the surface of particles, namely 3,4-benzpyrene is a condensed aromatic hydrocarbon with carcinogenic properties, i.e. can cause cancer when applied to the skin or when applied under the skin of animals.

The harmful effect of dust on the human body is determined by its content in the air of working premises, ie the concentration of dust, which can usually vary from 10 -8 to 10 5 mg / m 3. Increased dust concentrations cause intense harmful effects on the human body.

According to the degree of exposure to the human body, harmful substances (including aerosols) are divided into 4 hazard classes:

1st - extremely dangerous substances;

2nd - highly hazardous substances;

3rd - moderately hazardous substances;

4th - low-hazard substances.

Hazard Class harmful substances set depending on the norms and indicators.

The assignment of a harmful substance to a hazard class is carried out according to an indicator whose value corresponds to the highest hazard class. It should also be borne in mind that some industrial dusts are explosive.

One of the dangerous dusts for the human body on sea transport is grain dust, which consists of organic components.

(bacteria, spores, etc.) and inorganic (particles of sand, clay, soil). The content of silicon dioxide in grain dust reaches 10%.

Prolonged contact with grain dust can lead to the development of pneumoconiosis. With short-term exposure to the mucous membrane of the eyes, upper respiratory tract irritation and development of inflammatory processes are caused. When mechanical stress blistering eruptions ("grain scabies") appear on the skin, possibly also bacteriological lesions with severe headache, chills, palpitations, dizziness and nausea ("grain fever").

To prevent the harmful effects of industrial dust

a set of measures is used on the human body:

The maximum permissible concentration (MPC) of various dust in the air of the working area is developed and established;

Designed and installed ventilation units and aspiration systems;

Personal protective equipment is developed and applied;

III. BASIC OPERATIONS AND CALCULATIONS FOR THE ANALYSIS OF DUST IN THE WORK ROOM

a) Dust test protocol

b) Assessment of dustiness of the workplace / room

1. For a quantitative assessment of a dusty working room, it is necessary to know the mass of dust per unit volume. The dust concentration can be determined different methods, the most simple and reliable is the weighing one. The essence of the method lies in weighing a special filter before and after pulling a known volume of dusty air through it.

where: C is the concentration of dust in the air, mg / m 3;

Р 1 - filter mass before dust extraction, mg;

Р 2 - filter mass after dust collection, mg;

V 0 - air volume at the sample site, о С.

V o \u003d

where: V is the volume of air drawn through the filter under the conditions of the experiment (at t (o C) and pressure B (hPa);

There are many industry documents covering dusty indoor environments. These are SNIPs, GOSTs and they consider it from their own professional points of view. But nowhere in them there are no figures limiting the content of dust in household and office premises. This is primarily due to the fact that the most different materials... Namely, from the used finishing materials, materials used in the equipment of premises and construction of premises (ventilation and air conditioning). And having established standards for dust for household and office space designers run the risk of not meeting them.

In 2004, the broadest document was put into effect, which defines the standards for the content of dust in the air. This is "Interstate standard GOST ISO 14644 -1-2002, Cleanrooms and associated controlled environments, Part 1, Classification of air purity".

Here is such a long and uncomplicated name. For us, in this case, the table is interesting. 1.from section 3.

Previously, there was GOST R 50776-95, which differs by standardizing the content of microorganisms (see Table 1, the pink-highlighted column), and the values \u200b\u200bof the amount of dust are not rounded.

Considering that we need guidelines for dust concentration, the data of these two GOSTs are summarized in one table.

Table 1, airborne particle cleanliness classes for clean rooms and clean areas

nk - the counting concentration of particles of a given size for a given class is not controlled,

nd - particles of the given and bigger size shouldn't be in the air

MK - the maximum permissible number of microorganisms, pcs / m 3

I have not yet found data related to the category of air cleanliness in domestic and office premises. Although I have come across standards for clean rooms in medical institutions.

Knowing about the strict standardization of the dust content in the air of clean industrial premises with a category, we can conclude that classes (categories) 7, 8, 9 are closest to office (7, 8) and domestic (9) premises.

Conclusion

Although GOST defines the category "for clean rooms and clean areas" we are interested in ISO class 9, as (in my opinion) the closest to domestic premises and ISO Class 7 and 8 for office premises equipped with air conditioning and air filtration, respectively.

The figures given can only be used as guidelines when carrying out estimated calculations for air filters electronic and computing technology and its operating regulations.

For accurate calculations, the values \u200b\u200bof the dust levels indicated in the passports of the premises where the equipment is located should be used.

Prepared by A. Sorokin,

Methods for determining air dust content

The dustiness of the air can be determined by gravimetric (weight), counting (microscopic), photometric and some other methods.

Removal of dust from the air can be carried out in various ways: aspiration, based on air sucking through a filter; sedimentation, based on the process of natural deposition of dust on glass plates or jars, followed by counting the mass of dust that has settled on 1 m of the surface; with the help of electrodeposition, the principle of which is that a high-voltage electric field is created in which dust particles are electrified and attracted to the electrodes.

In sanitary and hygienic practice, the gravimetric method is adopted as the main method for determining dust content, because with a constant chemical composition, the mass of dust is of primary importance, it remains in the human body. Determination of only the mass of dust does not give a complete picture of its harmfulness to humans and the technological process, since with the same mass there can be different chemical and particle size distribution of dust, which affects its impact on humans, equipment and technology. The complete characteristic of dust consists of its mass, contained in a unit volume of air, chemical and dispersed composition.

The counting (microscopic) method makes it possible to determine the total amount of dust particles per unit volume of air and the ratio of their sizes. To do this, dust contained in a certain volume of air is deposited on glass covered with a transparent adhesive film. The shape, quantity and size of dust particles are determined under a microscope.

The quality characteristic of dust is determined photometrically using a current ultraphotometer, which detects individual dust particles using strong side light.

To separate dust from air, various filters are used that retain dust particles with a size of 0.1 microns or more, depending on the pore size of the filter. These filters are available in many countries. The filter material can be different depending on its purpose: cellulose, synthetic materials, asbestos (for the determination of combustible dust particles). Combined filters are also used. Special filters impregnated with immersion oil are produced, which makes them transparent - this allows additional microscopic examination of dust.

In Ukraine, AFA (analytical aerosol filter) filters of round shape with filtration planes 3 are most often used; 10, 20 cm2, which have a support ring, a filter element and a protective paper ring with a protrusion. The filter element consists of a uniform layer of ultra-thin polymer fibers with or without gauze (Petryanov filter). Filters allow you to work with them without preliminary drying through the hydrophobic properties of the polymer.

Methods for normalizing the air composition of the working area

There are many different ways and measures designed to maintain the cleanliness of the air in industrial premises in accordance with the requirements of sanitary standards. They all boil down to specific measures:

1. Prevention of the penetration of harmful substances into the air of the working area by sealing equipment, sealing joints, hatches and openings, improving the technological process.

2. Removal of harmful substances that enter the air of the working area through ventilation, aspiration or cleaning and normalization of air using air conditioners.

3. The use of human protective equipment.

Sealing and sealing are the main improvement measures technological processesin which harmful substances are used or generated. The use of automation allows you to take a person out of a polluted room into a room with clean air. Improvement of technological processes allows replacing harmful substances with harmless ones, abandoning the use of dusty processions, replacing solid fuel for liquid or gaseous, install gas, dust collectors in the technological cycle, etc.

If the technology is imperfect, when it is not possible to avoid the penetration of harmful substances into the air, they are intensively removed using ventilation systems (gas, steam, aerosols) or aspiration systems (solid aerosols). Installation of air conditioners in rooms where there are special requirements for air quality creates normal microclimatic conditions for workers.

Special requirements are imposed on the premises where work is carried out with hazardous substances that generate dust. So, the floor, walls, ceiling should be smooth, easy to clean. In workshops where dust is emitted, wet or vacuum cleaning is regularly done.

In rooms where it is impossible to create normal conditions corresponding to microclimate standards, personal protective equipment is used (313).

According to GOST 12.4.011-87 "Occupational safety and health equipment. Classification", all 313, depending on the purpose, are divided into the following classes: insulating suits, respiratory protection, special protective clothing, leg protection, hand protection, head protection, face protection, eye protection, hearing protection, fall protection and other precautions, dermatological protective equipment, complex protective equipment.

Effective use of 313. depends on their the right choice and operating conditions. When choosing, it is necessary to take into account the specific production conditions, the type and duration of exposure to the harmful factor, as well as the individual characteristics of a person. Only the correct use of the 313 can protect the worker as much as possible. For this, employees must be familiar with the range and purpose of 313.

To work with toxic and pollutants, they use overalls - overalls, dressing gowns, aprons, etc.; for protection against acids and alkalis - rubber shoes and gloves. To protect the skin, hands, face, neck, protective creams and pastes are used: anti-toxic, waterproof, fat-resistant. Eyes from possible burns and aerosols are protected by glasses with sealed frames, masks, helmets.

Respiratory personal protective equipment (RPE) includes respirators, industrial gas masks and self-contained breathing apparatus used to protect against harmful substances (aerosols, gases, vapors) in the ambient air.

According to the principle of operation, RPEs are subdivided into filtering (used if there is at least 18% free oxygen in the air and a limited content of harmful substances) and insulating (if the oxygen content in the air and an unlimited amount of harmful substances is insufficient for breathing).

Filtering RPEs are divided into:

anti-dust - for protection against aerosols (respirators ShB-1, "Lepestok", "Kama", "Snezhok", U-2K, RP-K, "Astra-2", F-62Sh, RPA, etc.);

gas masks - to protect against gas-vapor-like harmful substances (respirators RPG-67A, RPG-67V, RPG-67KD, gas masks of brands A, B, KD, G, E, CO, M, BKF, etc.);

gas and dust protection - to protect against steam and gas-like and aerosol harmful substances at the same time (Respirators Ru 60M, "Snezhok PG", "Lepestok-G");

isolating devices - there are hose and autonomous.

Isolating hose devices are designed to operate in an atmosphere containing less than 18% oxygen. They have a long hose that delivers breathing air from the clean area. Their disadvantages are that the breathing hose interferes with work, does not allow free movement (PSh-I hose gas mask without forced air supply, hose length 10 m; PSh-2 with an air blower - provides work for two people at the same time, hose length 20 m; respirator for artists RMP-62; pneumatic helmets LIZ-4, LIZ-5, myotome-49 - work from a compressor air line).

Self-contained breathing apparatus operate from an autonomous chemical source of oxygen or from cylinders with air or breathing mixture. They are designed to perform rescue operations or to evacuate people from a gas-polluted area.

Small-sized mine samoryativiik ShSM-1. Has a chemical source of oxygen. The term of use is 20-100 minutes, depending on the intensity of oxygen consumption (energy consumption), weight 1.45 kg.

Insulating auxiliary respirator RVL-1. Has a compressed oxygen cylinder and a regenerative chemical cartridge for oxygen regeneration. Opens 2:00, weight 9 kg.

Respirator "Ural-7". The principle of operation is the same as in the RVL-I respirator, but it is more dimensional. Operates at 5:00, weighs 14 kg. Worn over the shoulders, mass cushioning device for easy wearing.

The R-30 respirator has the same life support system as above. Designed for 4:00 action, weighs 11.8 kg.

The ASV-2 breathing apparatus consists of 2 air cylinders, a mask or mouthpiece, a hose, a reducer, has a pressure gauge to control air pressure, a safety valve, etc. Designed to protect the respiratory system in a polluted atmosphere.

produced by an aspiration weight (gravimetric) method using an electric aspirator (Fig. 2).

Fig. 2. Electric aspirator for taking single dust samples

Dust is a dispersed system, where a fragmented substance (dispersed phase) is in a continuous dispersed medium, i.e. these are suspended in air, slowly settling solid particles ranging in size from 0.001 to 100 microns or aerosol.

The principle of operation of the electric aspirator is to draw a certain volume of air through the aspirator

torus with deposition of dust particles on a paper filter. The method is based on capturing dust from the air sucked through the filter at a standard aspiration rate of 10-20 l / min. with subsequent conversion to 1 m 3 of air (1 m 3 \u003d 1000 l). Air analysis can be carried out both in samples taken once (the sampling time is 15-20 minutes), and repeatedly at least 10 times a day at regular intervals with averaging of the obtained data (the frequency of sampling during the day determines the boron to assess the type of MPC - daily average or maximum one-time). Air sampling is performed in the breathing zone. For sampling, the filter is fixed in the allonge (cartridge) of the electric aspirator, air is passed through it at a rate of 20 l / min. ( V ) for 10 minutes. ( T ). The volume of the taken air sample is calculated by the formula:

υ \u003d T V,

where T - sampling time, min., V - sampling rate, l / min. A non-hygroscopic aerosol filter, which is ultra-thin polymer fibers, fixed in a paper ring, is weighed on an analytical balance with an accuracy of 0.1 mg to ( A 1 ) and after ( A 2 ) air sampling. Dust content X in 1 m 3 of air is calculated by the formula:

X \u003d [(A 2 - A 1) 1000] / υ,

where X - dust content in the air, mg / m 3; A 1 and A 2 - filter weight before and after sampling, mg; υ − air volume, l.

For a hygienic assessment of air pollution with dust, the established dust content is compared with the maximum or average daily MPC of non-toxic dust in the ambient air; characterize dispersed and chemical composition, morphological structure, electrical state, nature (organic, inorganic, mixed) and the mechanism of formation (disintegration or condensation aerosol).

Hygienic standards for dust for atmospheric air

- maximum one-time MPC mr 2 \u003d 0.5 mg / m 3,

- average daily MPC s / s 3 \u003d 0.15 mg / m 3.

In the premises of health care facilities, the requirements for the content of dust in the air are determined by the classification of premises by cleanliness and are limited to a particle size of 0.5 microns and 5.0 microns.

In industrial premises: MPC for non-toxic dust \u003d 10 mg / m 3, MPC for dust containing free silicon dioxide \u003d 1-2 mg / m 3.

3. Determination of microbial air pollutionosu-

it is carried out by the aspiration method in the modification of Krotov. The Krotov apparatus is an aspirator with a removable cover. The test air is sucked in at a rate of 20-25 l / min. through the wedge-shaped slot in the lid of the device. When moving the Krotov apparatus from one room to another, its surface is treated with a disinfectant solution. An air sample is taken for 10 minutes. ( T ) with a rate of 20 l / min ( V ). The volume of the sampled air is calculated by the formula.

Methods for determining air dust content are divided into two groups:

With the release of a dispersed phase from aerosol - weight or mass (gravimetric), counting (conimetric), radioisotope, photometric;

Without separation of the dispersed phase from the aerosol - photoelectric, optical, acoustic, electrical.

The basis for the hygienic regulation of the dust content in the air of the working area is the weight method. The method is based on pulling dusty air through a special filter that retains dust particles. Knowing the mass of the filter before and after sampling, as well as the amount of filtered air, calculate the dust content per unit volume of air.

The essence of the counting method is as follows: a certain volume of dusty air is sampled, from which dust particles are deposited on a special membrane filter. After that, the number of dust grains is counted, their shape and dispersion are examined under a microscope. The dust concentration in the counting method is expressed by the number of dust particles in 1 cm 3 of air.

The radioisotope method for measuring dust concentration is based on the property of radioactive radiation (usually α-radiation) to be absorbed by dust particles. The dust concentration is determined by the degree of attenuation of radioactive radiation when passing through a layer of accumulated dust.

The Ministry of Health and Social Development approved regulatory documents for determining the dust content:

MU No. 4436-87 "Measurement of aerosol concentrations with predominantly fibrogenic action";

MU No. 4945-88 "Guidelines for the determination of harmful substances in welding aerosol (solid phase and gases)".

Measurement of dust content by weight (gravimetric) method

When measuring the dust concentration, the pre-weighed "clean" filter AFA-VP-20 (AFA-VP-10) is fixed in a cartridge (allonge), which is connected with a hose to an aspirator PU-3E and an amount of air is drawn through the filter so that the sample of the captured dust is from 1.0 to 50.0 mg (for AFA-VP-10 from 0.5 to 25.0 mg).

The analytical aspiration filter (AFA) is made of filter cloth FPP-15, which has a charge of static electricity. The use of analytical filters of the AFA type allows you to analyze the air environment with a high degree of accuracy. They have high retention capacity, low aerodynamic resistance to air flow, high throughput (up to 100 l / min), low weight, low hygroscopicity, the ability to determine the concentration of dust regardless of its physical and chemical properties. For ease of handling, the edges of the filters are pressed and placed in protective casings (Fig. 2).

Fig. 2. Filter type AFA

1 - filtration material; 2 - protective clip

Aspirators are used for sampling. Methods and equipment used to determine the concentration of dust must ensure the determination of the value of dust concentration at the level of 0.3 MPC with a relative standard error not exceeding ± 40% at 95% probability. At the same time, for all types of samplers, the relative standard error of determining dust at the MPC level should not exceed ± 25%. For sampling it is recommended to use filters AFA-VP-10, 20, AFA-DP-3.

After sucking in the dusty air, the filter is removed from the allonge, re-weighed on an analytical balance with an accuracy of 0.1 mg, and the weight of the sample of dust ΔР on the filter is determined by the difference in the masses of the “clean” and “dirty” filters.

Dust concentration under working conditions:

, mg / m 3 (1)

where ΔР \u003d Р к - Р n is the mass of dust caught by the filter, mg; R n and R to - the mass of the AFA filter, respectively, before and after aspiration, mg; V deputy - the volume of air from which the dust was separated on the filter, m 3.

Simultaneously with air sampling for dustiness, the temperature (T, 0 C) and air pressure (B, mm Hg) are measured to bring the air volume under operating conditions V deputy, from which the dust on the filter was isolated, to standard conditions (760 mm Hg . Art. and 20 0 С):

, m 3 (2)

Then the concentration of dust in the air under standard conditions:

, mg / m 3 (3)

The results of measurements and calculations are used for the sanitary and hygienic assessment of the air in the working area by the dust factor, correlating with the maximum permissible concentrations (MPC), as well as for determining the effectiveness of methods and means of combating dust.