Calculation of the required air exchange. Ventilation design recommendations

Ventilation air volume is determined for each premise separately considering concentration of harmful substances. Alternatively, ventilation air volume calculated 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. * A_ch [m³/h],

where V_prem. – premise volume [m³];

A_ch – 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 recommended ventilation rate.

Calculation of air exchange according to number of inhabitants:

L = L₁ * N_L (m³/hour),

where L₁ – rated value for air volume per one person, m³/h*person;

N_L – 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 / ((d_v-d_n) * ρ) (m³/hour)

where D – moisture, g/hour

d_v – moisture content in the exhaust air, gram of water/kg of air

d_n – moisture content in the intake air, gram of water/kg of air

ρ – air density, kg/m³ (at 20 °C = 1.205 kg/m³)

Calculation of air exchange to remove excessive heat:

L= Q / (ρ * C_p*(t_v-t_n)) (m³/hour)

where Q – heat emission in the premises, kW

t_v – exhaust air temperature, °С

t_n – intake air temperature, °С

ρ – air density, kg/m³ at 20°С = 1.205 kg/m³);

C_p – heat capacity of air [kJ/(kg.K)] at 20°С; C_p=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 1m² 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
Storeroom	1
Garage	4-8
Cellar	4-6

Industrial premises and large premises	Premise 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= G_CO2 / (U_PDК-U_P) (m³/hour)

де G_СО2 – СО₂release amount [l/hour]

U_PDК – СО₂ maximum permissible concentration, l/m³

U_P – gas concentration 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

L = Vprem. * Ach [m³/h],