This may help to understand what is going on:
Most all office buildings, hotels and hospitals are sealed systems. The building code says that the HVAC (Heating, Ventilation and Cooling) system must have so many complete air exchanges per day. That is the entire volume of air should be replaced by fresh air so many times a day (numbers vary by the state). This is accomplished by an outside air inlet and controlled by a damper. Even the hotels that have individual AC in the rooms have vents to accomplish such task.
Now, if you exchange the inside hot or coll air with outside cool or hot air (respectively due to winter or summer) then there is a large energy use to do that. So, even though it is against regulation, the building people do not set it up correctly to save money (lots of money). Some places it is completely closed off hoping no one will notice. In large hotels, you have to stay there more than two days under this scenario to see you are getting a headache. If you have any suspicions, and happen to call the local health department, they normally setup schedules for check up. By that time it is all fixed.
My recommendation:
1. Hotels with independent room AC: Crack open the window about one centimeter (pinkie finger) - should do it. If the windows do not open, you have to open the top cover of the AC and find the vent control and set it to open position.
2. Office you work at: If it feels stuffy on mondays - it is bad. By mid week, the vent is open very little. Complain to the building maintenance to check it out.
3. Hospitals: Do not go near a hospital unless your life depends on it - then you take a gamble. Hospitals in south are worse due to moisture. I can not help here.
4. Home: In winter time, the home is air tight. So open an window time to time to get some fresh air. Use the bathroom and kitchen power vent if they are vented outside. Then you can crack open one window to get fresh air. To reduce the chances of bacteria and viruses, you can install a germicidal lamp inside your air return system that can kill any airborne bugs. If you install one, leave it all winter long on.