Ventilation
The process by which fresh air is introduced, in this case to an enclosed space, and contaminated
air is removed from that same space is termed ventilation. There are two common methods of
ventilation used:
· When the process occurs by natural means of wind effect and difference between the
inside and outside temperatures creating pressure differentials, through an open window
or ventilation panel, it is called natural ventilation
· When is the process is driven by mechanical fans to provide controlled ventilation to a
system, it is called mechanical ventilation or forced ventilation.
The reasons for providing ventilation are:
· Legal requirements
· Dilute contaminants and removing them from the space
· To remove products of respiration (odours, CO2)
· To provide a continuous supply of oxygen
· To create an adequate air movement for human comfort
According to the Buildings Department in Hong Kong [7] there is a requirement of 1,5 ACH in
residential buildings, if the process is by means of natural ventilation. However, for kitchens an
additional 5 ACH by means of mechanical ventilation should be provided.
For PRC there is a recommendation of 0,5 ACH to 1 ACH depending on what source is used for
obtaining the design conditions. The ASHRAE standard [4] is often referred to in Hong Kong
and according to the standard, concerning mechanical ventilation 10 l/s/person of air should be
provided. The VM1 unit has 3 settings, MIN, NORM and MAX that provides constant airflow
depending on how many ACH is required. The MIN setting is used when there are no people
present, NORM setting is used for normal operation, and the MAX is used for forced ventilation.
The fans for supply and discharge can be set to different speeds and be used to fine-tune the
system. In this paper, the system was set to be balanced. Another consideration is the placement
of the fresh air intake and the discharge extract air. These must be placed with enough space
between them so that the discharge extract air will not pollute the fresh air.
The process by which fresh air is introduced, in this case to an enclosed space, and contaminated
air is removed from that same space is termed ventilation. There are two common methods of
ventilation used:
· When the process occurs by natural means of wind effect and difference between the
inside and outside temperatures creating pressure differentials, through an open window
or ventilation panel, it is called natural ventilation
· When is the process is driven by mechanical fans to provide controlled ventilation to a
system, it is called mechanical ventilation or forced ventilation.
The reasons for providing ventilation are:
· Legal requirements
· Dilute contaminants and removing them from the space
· To remove products of respiration (odours, CO2)
· To provide a continuous supply of oxygen
· To create an adequate air movement for human comfort
According to the Buildings Department in Hong Kong [7] there is a requirement of 1,5 ACH in
residential buildings, if the process is by means of natural ventilation. However, for kitchens an
additional 5 ACH by means of mechanical ventilation should be provided.
For PRC there is a recommendation of 0,5 ACH to 1 ACH depending on what source is used for
obtaining the design conditions. The ASHRAE standard [4] is often referred to in Hong Kong
and according to the standard, concerning mechanical ventilation 10 l/s/person of air should be
provided. The VM1 unit has 3 settings, MIN, NORM and MAX that provides constant airflow
depending on how many ACH is required. The MIN setting is used when there are no people
present, NORM setting is used for normal operation, and the MAX is used for forced ventilation.
The fans for supply and discharge can be set to different speeds and be used to fine-tune the
system. In this paper, the system was set to be balanced. Another consideration is the placement
of the fresh air intake and the discharge extract air. These must be placed with enough space
between them so that the discharge extract air will not pollute the fresh air.
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