Difference between minimum outdoor air changes and minimum total air changes

[Fakhr E Alam]

Hi there,

Can anyone explain to me difference between minimum outdoor air changes and minimum total air changes in ASHRAE-Design Parameters-Hospital Spaces.

[Brian_UK]

It is as per the descriptions given.

Minimum total air changes per hour (ACH) is the least number of times the total air within the space must be changed per hour.

Within the above minACH the amount of fresh air to be changed per hour is also given/required.

So if there is a need for minACH of 10 you need and airflow rate that will change the volume of air within the space 10 times.

Likewise if they want a fresh air minACH of 15 then you need to ensure that the fresh air is changed 15 times per hour.

[Josip]

Hi there,

Can anyone explain to me difference between minimum outdoor air changes and minimum total air changes in ASHRAE-Design Parameters-Hospital Spaces.

Hi,

I am not sure, but I believe that within minimum total air changes per hour (an example 20 times for surgical rooms) there must be minimum 4 outdoor air changes i.e. with outdoor fresh air ...

what is correct, we need to replace exhausted air with fresh outdoor air full of oxygen ...


But, I can be wrong too ...

Best regards, Josip :)