I used to wonder why I’m having this issue after sleeping in an air conditioned room wondering when I didn’t have an air-conditioner, I never faced this problem. Recently I discovered, 𝘪𝘵’𝘴 𝘣𝘦𝘤𝘢𝘶𝘴𝘦 𝘵𝘩𝘦𝘳𝘦’𝘴 𝘯𝘰 𝘳𝘰𝘰𝘮 𝘧𝘰𝘳 𝘧𝘳𝘦𝘴𝘩 𝘢𝘪𝘳 𝘵𝘰 𝘦𝘯𝘵𝘦𝘳. To always maintain good health, fresh air is an essential thing. Smart air filters research in a closed space also shows the reduction of oxygen level by 0.3% by the end of the day. Here’s their link to the full article: (https://lnkd.in/dj6GwiTP). They show especially when we are in an air conditioned room, we have to ensure getting fresh air. The AC takes in the indoor air, cools it down and then releases it back into the room. As a result, at one point the fresh air inside the room decreases and the necessity of getting more fresh air from the outdoors arises. This is how the quality of the air inside an air conditioned room gets reduced. For this, it’s a must to add fresh air in the HVAC air handler or to open the windows even adjusting extractor fans, getting HRV and ERV etc.

There are different standards to design outdoor air intake flow rate for a ventilation system. For a US project, we follow the Uniform Mechanical Code 2021. Here the ventilation rate is depending on
Az= Zone from Area
Pz= Zone population
Rp= Outdoor airflow rate (per person per standard)
Ra= Outdoor airflow rate (per area per standard)

For example, a 1000 ft sq2 office area with 10 people would require at least 170 CFM of air as per this standard.