Determination of the Essential Air Exchange. Engineering recommendations
Calculation of air exchange according to air exchange rate:
Ventilation air volume is determined for each premise separately considering concentration of harmful substances. Alternatively, ventilation air volume cal culated be set according to the research results. If the nature and concentration of harmful substances is not possible to determine, air exchanged is calculated as following:
L = V prem * Ach [m3/h],
where V prem. – premise volume [m3];
Ach – minimum air exchange per hour, refer air exchange table.
How to determine a premise volume?
Use a simple formula:
length x width x height = volume of the premises in cubic meters
A x B x H = V [m3]
Example: a premise with 7 m length, 4 m width and 2.8 m height. To determine the air volume required for ventilation of this premises, calculate the room volume 7x4x2.8=78.4 m3. After that determine the required efficiency of the fan using the following tables of reco mm ended ventilation rate.
Calculation of air exchange according to number of inhabitants:
L=L1*NL [m3/hour]
where L1 – rated value for air volume per one person, m3/h*person;
NL – number of inhabitants in the premises
20-25 m3/h per one person at low physical activity
45 m3/h per one person at light physical activity
60 m3/h per one person at heavy physical activity
Calculation of air exchange with vapor emission:
L= D / ((dv-dn) * ρ) [m3/hour]
where D – moisture, g/hour;
dv – moisture content in the exhaust air, gram of water/kg of air;
dn – moisture content in the intake air, gram of water/kg of air;
ρ – air density, kg/m3 (at 20 °С = 1.205 kg/m3);
Calculation of air exchange to remove excessive heat:
L= Q / (ρ * Cp*(tv-tn)) [m3/hour]
Q – heat emission in the premises, kW;
tv – exhaust air temperature, °C;
tn – intake air temperature, °C;
ρ – air density [kg/m3] at 20°С = 1.205 kg/m3;
Cp – heat capacity of air [kJ/(kg.K)] at 20 °С; Cp=1.005 kJ/(kg.K)
Air ventilation rate:
| Domestic premises | Air exchange rate | |
|---|---|---|
| Living room of apartments or hostel residential premises | 3 m3/h for 1 m2 in residential premises | |
| Kitchen in flat or hostel | 6-8 | |
| Bathroom | 7-9 | |
| Shower cabin | 7-9 | |
| WC | 8-10 | |
| Home laundry room | 7 | |
| Cloakroom | 1,5 | |
| Storerooms | 1 | |
| Garage | 4-8 | |
| Cellar | 4-6 |
| Industrial premises and large premises | Air exchange rate | |
|---|---|---|
| Theatre, cinema, confrence hall | 20 40 m3 per each visitor | |
| Office | 5-7 | |
| Bank | 2-4 | |
| Restaurant | 8-10 | |
| Bar, café, pub, billiard room | 9-11 | |
| Professional kitchen | 10-15 | |
| Supermarket | 1,5-3 | |
| Chemist’s | 3 | |
| Garages and vehicle repair shops | 6-8 | |
| Public WC | 10 12 (or 100 m3 per each WC pan) | |
| Dance halls and disco clubs | 8-10 | |
| Smoking rooms | 10 | |
| Server rooms | 5-10 | |
| Sport hall | 80 m3 or more for each sportsman and 20 m3 or more for each viewer | |
| Hair dresser's up to 5 working places | 2 | |
| Hair dresser's more than 5 working places | 3 | |
| Warehouses | 1-2 | |
| Laundryroom | 10-13 | |
| Swimming pool | 10-20 | |
| Industrial painting shop | 25-40 | |
| Machine shop | 3-5 | |
| School classroom | 3-8 |
Calculation of air exchange depending on maximum permissible concentration of aggressive substances in the air:
L= GCO2 / UPDK-UP [m3/hour]
GCO2 – CO2 release amount [l/hour],
UPDK – CO2 maximum permissible concentration, l/m3,
Up – gas content in the intake air, l/hour.
| CO2 permissible concentration norms, l/m3 | ||||
|---|---|---|---|---|
| Permanent residential premises | 1,0 | |||
| Hospitals and child care centers | 0,7 | |||
| Periodically occupied premises | 1,25 | |||
| Short stay premises | 2,0 | |||
| Open air: | Populations centers (village) | 0,33 | ||
| Small towns | 0,4 | |||
| Big cities | 0,5 | |||
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