Air humidity in the apartment: the norm for residential premises. Air humidity. Preparing for the Unified State Exam Absolute and relative humidity
Physics teacher Kokovina L.V.
Rybinsk municipal district
Air humidity. Preparation for the Unified State Exam.
Part A
Relative air humidity 50%. Compare the readings of the wet (T 1) and dry (T 2) thermometers of the psychrometer.
A).T1=T2; B). T1>T2 B) T1
2. Determine the absolute and relative humidity at a temperature of 16 0 C, if the dew point is 10 0 C. The saturation vapor pressure of water at the indicated temperatures is respectively: 1.81 kPa and 1.22 kPa.
A).1.22kPa,67% B).1.81kPa,67% C). 1.22kPa,33% G).1.81kPa,33%
3. There are two sealed vessels with air in the room. In the first of them relative humidity equal to 40%, in the second 60%. Compare the water vapor pressure in these vessels. The air density in both vessels is the same.
A).P1=P2 B)P1>P2 C)P1
4. The pressure of water vapor in the atmosphere at 15 0 C was 1.5 kPa. Will dew fall if the air temperature drops to 10 0 C at night? The saturated vapor pressure at 10 0 C is 1.22 kPa.
A) Will drop B) Will not drop C) The answer is ambiguous
5. In a classroom at a temperature of 25 0 C, it is created high humidity air. How will the air humidity in the room change if you open the window, but it’s cold and raining outside?
A) Will increase B) Will decrease C) Will not change D) The answer is ambiguous
6. There is saturated steam in a sealed vessel. How will the pressure of this steam change if the temperature is increased by 2 times?
A) Will not change B) will increase by 2 times C) Will increase by more than 2 times D) The answer is ambiguous
IN 1. The wet thermometer of the psychrometer shows 10 0 C, and the dry thermometer 14 0 C. Find the relative humidity and partial pressure of water vapor. The use of a physics reference book is provided.
C1. In one vessel with a volume of 10 liters there is air with a relative humidity of 40%, and in another vessel with a volume of 30 liters there is air at the same temperature, but at a relative humidity of 60%. The vessels are connected by a thin tube to a tap. What relative humidity (in percent) will be established after opening the tap?
Saturated and unsaturated steam
Let's take a closed vessel with liquid and keep the temperature constant. After some time, a thermodynamic equilibrium of evaporation and condensation processes will be established in such a vessel. That is, the number of molecules that leave the liquid will be equal to the number of molecules that return to the liquid.
Definition
A gaseous substance that is in equilibrium with its liquid is called saturated vapor.
Definition
Unsaturated steam is steam whose pressure and density are less than the pressure and density of saturated steam.
Saturated vapor pressure increases with increasing temperature.
There is always some mass of water vapor in the air around us. Air that contains water vapor is called humid air. In atmospheric air, the intensity of water evaporation depends on how different the water vapor pressure is from the saturated vapor pressure at a given temperature.
Absolute and relative humidity
Use the concepts of absolute and relative humidity.
Definition
Absolute humidity is the mass of water vapor found in one cubic meter of air.
Absolute humidity can be measured by the partial pressure of water vapor (p) at some temperature (T). With respect to partial pressure, Dalton's law is satisfied, which states that the individual components of a mixture of gases are considered independent. Therefore, each component creates pressure:
and the total pressure is equal to the sum of the pressures of the components:
where $p_i$ is the partial pressure of the i gas component. Equation (2) is Dalton's law.
Using the fact that humidity is the amount of water vapor in air (gas), the concept of partial pressure and Dalton's law can be very useful in the practical consideration of questions about absolute humidity.
Absolute humidity is also called the density of water vapor ($\rho $) at the same temperature (T). With an increase in absolute humidity, water vapor approaches the state of saturated steam. The maximum absolute humidity at a given temperature is the mass of saturated water vapor in one cubic meter of air.
Definition
Relative humidity is the ratio of absolute humidity to the maximum absolute humidity at a given temperature.
It is expressed as a percentage:
\[\beta =\frac(\rho )((\rho )_(np))\cdot 100\%=\frac(p)(p_(np))\cdot 100\%\ \left(1\right ),\]
where $(\rho )_(np)-$saturated vapor density at a certain T, $p_(np)$-saturated vapor pressure at the same temperature. When thermodynamic equilibrium of the processes of evaporation and condensation is established, the relative humidity is 100\%. This means that the amount of water in the air does not change.
With isochoric cooling or isothermal compression, unsaturated steam can be converted into saturated steam. The temperature ($T_r$) at which steam becomes saturated is called the dew point. $T_r$ is the temperature of thermodynamic equilibrium of vapor and liquid in air (gas). For $(T
Air humidity is measured with special instruments - hygrometers, psychrometers. A relative humidity of 40% to 60% is considered optimal for humans at a temperature of about 20 degrees Celsius. To solve practical problems, lookup tables are often used, which indicate the pressure and density of saturated water vapor at various temperatures.
Example 1
Assignment: Determine the saturated vapor pressure at temperature $T$ and a pressure of one atmosphere, if the mass of moist air at relative humidity $\beta $ in volume $V$ is equal to $m$ under the same conditions.
As a basis for the solution, we will take Dalton’s law, which for a mixture of gases, and here we have a mixture of dry air and water vapor, will be written in the form:
where $p_v$ is the pressure of dry air, $p_(H_2O)$ is the pressure of water vapor.
In this case, the mass of the mixture is equal to:
where $m_v-\ $mass of dry air, $m_(H_2O)$- mass of water vapor.
We use the Mendeleev-Claiperon equation and write it for the component - dry air in the form:
where $(\mu )_v$- molar mass air, $T$ - air temperature, $V$ - air volume.
For water vapor, taking it to be an ideal gas, we write the equation of state:
where $(\mu )_(H_2O)$ is the molar mass of steam, $T$ is the temperature of steam, $V$ is the volume of steam.
Relative humidity is:
\[\beta =\frac(p_(H_2O))(p_(np))\cdot 100\%\ \left(1.5\right),\]
where $p_(np)$ is the saturated vapor pressure. From (1.5) we express the saturated vapor pressure, we obtain:
Let us express the mass of dry air from (1.2), we obtain:
From (1.1) we express the pressure of dry air, we have:
Substituting (1.7) and (1.8) into (1.3), we get:
\[\left(p-p_(H_2O)\right)V=\frac(\left(m-m_(H_2O)\right))((\mu )_v)RT\ \left(1.9\right).\ ]
Let us express the mass of steam from (1.4), we obtain:
\[(m_(\ ))_(H_2O)=\frac(V\cdot p_(H_2O)(\cdot \mu )_(H_2O))(RT)\ \left(1.10\right).\]
Let us express the vapor pressure ($p_(H_2O)$) using expressions (1.9) and (1.10), we obtain:
\[\left(p-p_(H_2O)\right)V=\frac(\left(m-\frac(V\cdot p_(H_2O)(\cdot \mu )_(H_2O))(RT)\right ))((\mu )_v)RT\ \to pV(\mu )_v-p_(H_2O)V(\mu )_v=mRT-V\cdot p_(H_2O)(\cdot \mu )_(H_2O) \to V\cdot p_(H_2O)(\cdot \mu )_(H_2O)-p_(H_2O)V(\mu )_v=mRT-pV(\mu )_v\to p_(H_2O)=\frac(mRT -pV(\mu )_v)(V(\cdot \mu )_(H_2O)-V(\mu )_v)\ \left(1.11\right).\]
Using (1.6), we obtain the saturated vapor pressure:
Answer: The saturated vapor pressure under given conditions is equal to: $p_(np)=\frac(100)(\beta )\cdot \frac(mRT-pV(\mu )_v)(V(\cdot \mu )_(H_2O )-V(\mu )_v)$.
Example 2
Assignment: At temperature $T_1\ $the air humidity is equal to $(\beta )_1$. How will the air humidity change if its temperature becomes $T_2$ ($T_2>T_1$)? The volume of the vessel in which the gas was located is reduced by $n$ times.
In the problem it is necessary to find the change (difference) $(\beta )_2(-\beta )_(1,\ )$ relative humidity in the final and initial states:
\[(\triangle \beta =\beta )_2(-\beta )_1=(\beta )_(1\ )\left(\frac((\beta )_2)((\beta )_(1\ ) )-1\right)(2.1)\]
Using the definition of relative humidity we write:
\[(\beta )_(1\ )=\frac(p_1)(p_(np1))100\%,\] \[(\beta )_(2\ )=\frac(p_2)(p_(np2 ))100\%\ \left(2.2\right),\]
where $p_(np)$ is the saturated vapor pressure in the corresponding states, $p_1$ is the water vapor pressure in the initial state, $p_2$ is the vapor pressure in the final state.
Substituting (2.2) into (2.1) we get:
\[\triangle \beta =(\beta )_(1\ )\left(\frac(\frac(p_2)(p_(np2)))(\frac(p_1)(p_(np1)))-1\ right)=(\beta )_(1\ )\left(\frac(p_2p_(np1))((p_1p)_(np2))-1\right)\ \left(2.3\right).\]
Since, according to the conditions of the problem, we know the temperatures of the states of the system, we can consider the saturated vapor pressures ($p_(np1)$ and $p_(np2)$) known in this case, since we can always take them from the corresponding reference tables.
To find the pressures $p_1$ and $p_2$ we use the Mendeleev-Claiperon equation, taking into account that the amount of substance in the processes that occur in the system does not change, then we write:
\[\frac(p_2V_2)(p_1V_1)=\frac(T_2)(T_1)\left(2.4\right).\]
From the conditions of the problem it is known that the volume was reduced by $n$ times, that is:
\[\frac(V_2)(V_1)=\frac(1)(n).\]
Therefore, expression (2.4) will be written as:
\[\frac(p_2)(p_1n)=\frac(T_2)(T_1)\to \frac(p_2)(p_1)=n\frac(T_2)(T_1)\left(2.5\right).\]
Substituting (2.5) into (2.3), we get:
\[\triangle \beta =(\beta )_(1\ )\left(n\frac(T_2)(T_1)\frac(p_(np1))(p_(np2))-1\right).\]
Answer: For given processes, relative air humidity will change by $\triangle \beta =(\beta )_(1\ )\left(n\frac(T_2)(T_1)\frac(p_(np1))(p_(np2 ))-1\right)$
275. Please indicate the correct statements.
When a substance changes from a gaseous state to a liquid state at a constant temperature
276. At the same temperature, saturated water vapor in a closed vessel differs from unsaturated steam
277. There is unsaturated steam in the vessel under the piston. It can be made saturated
278. The dew point for water vapor in the room is 6°C. A dry bottle of water was brought into the room from the balcony, and soon it was covered with small droplets of water. It follows that
279. On Saturday the air temperature was higher than on Sunday. The partial pressure of water vapor in the atmosphere remained constant during these days. On which day was the relative humidity higher? Please note that saturated vapor pressure increases with temperature.
280. Choose the correct statements.
| A. | The dew point is the temperature at which the relative humidity becomes 100%. | |||||||
| B. | The pressure of saturated steam at a constant temperature does not depend on the volume it occupies. | |||||||
| IN. | Vapor that is in dynamic equilibrium with its liquid is called saturated. | |||||||
| 1) | A and B | 2) | B and C | 3) | A and B | 4) | A B C | |
281. The partial pressure of water vapor in air at 20°C is 0.466 kPa, the pressure of saturated water vapor at this temperature is 2.33 kPa. Relative air humidity is
283. The relative humidity in the room is 40%. What is the ratio between the partial pressure p of water vapor in the room and the pressure pH of saturated water vapor at the same temperature?
284. At the same temperature of 100°C, the pressure of saturated water vapor is 10 5 Pa, ammonia - 59 × 10 5 Pa and mercury - 37 Pa. In which of the answer options are these substances arranged in descending order of their boiling point in an open vessel?
285. The photograph shows two thermometers used to determine the relative humidity of the air using a psychrometric table in which humidity is indicated as a percentage.
Psychrometric table
| t dry term | Difference between dry and wet bulb readings | ||||||||
| °C | 7 | ||||||||
The relative humidity of the air in the room in which the shooting was carried out is equal to
The article examines in detail such a concept as air humidity in an apartment: the norm of this indicator for residential premises for various purposes, prescribed by GOST, the consequences for humans that arise as a result of deviations from the norm in one direction or the other. The text describes alternative ways moisture level measurements and those intended for this, as well as recommendations for maintaining optimal climatic conditions.
Air humidity in the apartment: normalwater content for comfortable living conditions
The optimal level of air humidity is one of the components that ensure comfortable climatic conditions for human habitation. Moreover, each room, depending on its purpose, has its own microclimate. Most often people care about temperature and quality air masses in the house, forgetting about this indicator. But it is the number of water (steam) molecules in the air that affects the perception of temperature by the human body, the safety of the indoor environment and the condition of plants.
Note! The generally accepted average normal air humidity in an apartment should be 45%. It may vary depending on the type of room and its operating conditions.
Deviation from the norm is possible, as in winter time year and during the warm period. In both cases, a lack or excess of humidity entails deterioration in human health, the condition of plants and damage to furniture, decoration, etc.
What should the humidity be in the apartment (average values for the main rooms):
| Room type | Humidity level, % |
| Dining room | 40-60 |
| Bathroom, kitchen | 40-60 |
| Library and work area | 30-40 |
| Bedroom | 40-50 |
| Children's | 45-60 |
Rooms such as the kitchen, bathroom and toilet will always have increased level moisture, so the standard for these rooms is higher than for other rooms.
What are the consequences of deviation?from humidity standards in the apartment: dry air
When the radiators are turned on, the indoor air becomes dry. As a result, the mucous membranes of the throat and nasal cavity become irritated in residents. Drying of hair and skin is observed. If the norm of humidity in a living space is violated, static electricity, raising dust particles into the air. This process can become the basis for the spread of germs and dust mites.
Excessive dryness of the room entails many negative consequences:
- decreased elasticity of the skin, nails and hair - as a result, dermatitis, peeling, microcracks and premature wrinkles appear;
- drying of the mucous membrane of the eyes - redness, unpleasant itching and sensation appear foreign bodies(“sand”);
- the blood thickens - because of this, blood circulation slows down, a person develops weakness and headaches. There is a decrease in performance, the heart is subjected to increased stress and wears out faster;
- the viscosity of intestinal and gastric juice increases - work digestive system slows down significantly;
- dryness of the respiratory tract - as a result, local immunity is weakened, and the likelihood of colds and infectious diseases increases;
- air quality decreases – air masses concentrate a large number of allergens that, at normal air humidity in the room, are bound by water particles.
Note! Plants and animals living near the apartment suffer from lack of moisture. The service life of wooden furniture and decoration is reduced, they fade and become cracked.
What are the consequences of exceeding the norm for indoor humidity?
An excess of water can also be dangerous for humans, so many people wonder what air humidity is considered normal in an apartment and how to maintain climatic conditions within this indicator. An increased content of water vapor in a room becomes an excellent breeding ground for fungi, mold and harmful bacteria.
In such conditions, many problems arise:
- The frequency and severity of respiratory diseases is increasing - diseases such as bronchitis, runny nose, allergies and asthma become chronic and difficult to treat.
- The microclimate in the rooms becomes unacceptable for life - people feel damp or stuffy in the rooms.
- The feeling of freshness is lost - the secretions of multiplying pathogenic organisms cause the appearance of unpleasant odors.
- The drying time for washed clothes increases.
Increased air humidity in the apartment is also harmful to the environment. Plants begin to rot, mold appears on the ceiling and walls, and wooden surfaces undergo deformation changes. Books and other paper products change their structure.
What should be the air humidity in the apartment?: standards according to GOST
Air humidity can be relative or absolute. To create comfortable climatic conditions in the house, the optimal value is calculated. GOST 30494-95 regulates an indicator indicating what the normal air humidity in an apartment should be.
Relative humidity is indicated as a percentage in the form of two values:
- optimal indicator;
- permissible value.
An acceptable value is a limit that does not harm human health, but can negatively affect general well-being, mood and reduce performance.
Note! If certain rules are provided for bedrooms, children's rooms and other areas where a person stays for a long time, then it is not necessary to strictly adhere to normal humidity in the kitchen, bathroom, corridor and toilet. These rooms are considered auxiliary.
The unit of measurement for absolute humidity is the actual vapor content in 1 m³ of air. For example, one cubic meter of air can contain 13 g of water. In this case, the absolute humidity will be 13 g/m³.
To obtain relative humidity, you will need to perform certain calculations. For this you need two indicators:
- the maximum possible water content in 1 m³ of air;
- the actual amount of water in 1 m³ of air.
The percentage of real data to the maximum possible value will be the relative humidity. For example, 1 m³ of air at a temperature of 24°C can hold a maximum of 21.8 g of liquid. If in fact there are 13 g of water present in it, then the relative humidity will be 60%. For convenience, you can use a special table of absolute air humidity, which contains auxiliary data.
Indicators of indoor air humidity standards according to GOST
The indicator prescribed by GOST depends not only on the purpose of the room, but also on the time of year. For the warm period, 30-60% is provided. In this case, the relative humidity in the room is 60 percent, and the maximum permissible will be 65%. For some regions where summer months accompanied by high humidity, normative meaning may be increased to 75%.
For the cold season, the standards for relative air humidity in the room are 40-45%. In this case, the maximum permissible value is 60%.
The most popular manufacturers and best models, Comparative characteristics structures, their advantages and disadvantages.
Normal air humidity in an apartment for a child
The child's immune system does not cope as effectively with negative impact factors environment like the body of an adult. Children overheat or freeze much faster, catch colds easily, suffer from infectious diseases and suffer more severely from them.
For this reason it is important to support optimal humidity air in the apartment for the child, especially in his room, where it is necessary to create conditions to maintain the baby’s immune strength.
In no case should the air in the children's room be dry. This atmosphere provokes intense loss of moisture from the baby’s body. Drying of the mucous membranes of the nasopharynx leads to their inability to resist viruses and infections. Your child may experience itchy eyes and flaky skin. For a child, the optimal air humidity in an apartment is considered to be between 50-60%.
According to Dr. Evgeniy Komarovsky, the value of normal air humidity in an apartment can be increased to 60% for healthy baby and 70% for a child who is sick infectious disease. The higher the humidity level, the less intensively the mucous membranes dry out.
Indicators of normal humidity in an apartment for a child’s body in winter are the same as for the warm season. However, there is one caveat here: Maximum temperature air in the room should not exceed 24°C. If the room is hotter, then a humidity of 60% will make it tropical. In practice in the heat high humidity it is more difficult to tolerate in an apartment than in the cold season.
Important! Exceeding 24°C in a children's room can lead to overheating of the baby's body. As a result, drying of the mucous membranes and loss of fluid will accelerate.
How to achieve optimal humidity in an apartment
The main factor influencing greatest influence to humidity, is temperature. The warmer the room, the more water capable of absorbing air. However, when calculating relative humidity, it is worth remembering that when high temperatures the volume of liquid in the same amount of air will be less. This nuance can be advantageously used to maintain humidity levels; the air outside in winter is very fresh and optimal parameters are ensured by ventilation.
Moisture is absorbed:
- appliances intended for heating;
- such interior items as toys, upholstered furniture, carpets;
- air conditioners.
Small sources of moisture can include plants and an aquarium, containers filled with water, wet laundry, a leaking roof or pipes.
How to determine air humidity in an apartment without device
To determine how much the air humidity level in the house has deviated, you can do without a special device and use:
- a glass of water;
- Assmann table;
- fir cone.
To determine the relative humidity of the air using a glass of water, it is necessary to cool the filled container in the refrigerator to 5°C. It will take about 3 hours for the water and the vessel to reach the specified temperature. After this, the glass is placed on the table away from the radiator. Within 5 minutes, condensation will form on the walls of the container.
Further results will depend on the behavior of this condensate:
- After a few minutes, the glass has dried - the humidity level has decreased.
- The condensation on the walls has not disappeared - the room has a normal microclimate.
- Drops flowed down the vessel in streams - there was an excess of moisture in the air.
A fir cone can serve as a measuring device. It should be placed away from heating devices and after a few hours the condition of the scales should be checked. If the air is too dry, the cone will open; if there is too much moisture, the scales will shrink tightly.
All of these devices only indirectly indicate the presence of a problem. To accurately determine the microclimate in a room, it is better to buy an air humidity sensor.
Helpful advice! Primary symptom Dry air is caused by dry tips of plants. Also, insufficient moisture levels can be determined by synthetic clothing, which in such conditions emits electrical charges.
Features of using a temperature and humidity sensor
To measure humidity, you can use special instruments called sensors or hygrometers. The device independently converts the received data and displays the result as a percentage.
Many people are looking for a solution, wondering how to remove humidity in an apartment. Exhaust fans are used to control the microclimate in the bathroom and other rooms with excess moisture. They prevent the formation of condensation on the walls and floor.
For residential premises, it is recommended to purchase a humidifier if there is a lack of moisture in the permanent basis. You will also need to additionally purchase air humidity sensors for the fan and humidifier, if these are not provided for in the designs of the devices themselves.
The operation of a hygrostat or sensor is based on the principle of a thermostat. The device opens and closes contacts in response to the amount of water vapor in the air. Thus, the operation of the fan or humidifier becomes automated. The device turns on only when it is needed.
Controlling humidity in an apartment: how to reduce/increase the amount of steam in the air
To control the amount of steam in the air, various methods are used, including improvised means. Their combination allows you to achieve a certain result.
How to get rid of humidity in an apartment:
- Ventilate the premises on a regular basis.
- Install exhaust fans where they are needed.
- Buy climate system or .
- Make timely repairs in the house (maintenance of plumbing and water supply).
- Use heating devices and air conditioners.
- Avoid drying clothes indoors.
- Install a powerful hood in the kitchen.
Helpful advice! In order for the hygrometer readings to be reliable, it is recommended to install this device deep in the room to eliminate the influence of drafts and other factors. or.
How to increase the humidity in a room:
- Buy a table fountain or aquarium (if no one in the household has asthma).
- Minimize the use of air conditioning and heating devices.
- Hang wet towels on radiators.
- From time to time, spray water with a spray bottle, thereby saturating the air with moisture.
- Do wet cleaning in the house regularly.
- Plant as many indoor plants as possible.
There are many devices that will allow you to achieve one or another result depending on your needs. They are selected taking into account the microclimate in the house. Before purchasing them, it is recommended to accurately set the humidity parameters. To do this, measurements are taken over several days.
Fits perfectly into the interior
You can maintain optimal humidity in your home using special devices– humidifiers. This category of climate control equipment includes many modifications: traditional, steam, ultrasonic devices. Air “washers” and climate control systems are more complex versions of these devices, equipped with a hygrometer, timer and other useful additions. An ultraviolet lamp will help in the fight against mold.