And if you live on the lower floors, it's even worse, according to a study by RDH.

Building more multi-unit residential buildings (MURBs) is critical for reducing transportation and for increasing affordability. But one of the big problems with most buildings in North America is ventilation. Most buildings rely on a pressurized corridor system, where a rooftop unit pumps air down into the corridors. This is supposed to be safer, as it keeps smoke from a fire in an apartment in the apartment, along with smells from cooking or smoking.

RDH Building Science

Each apartment usually then has a bathroom exhaust duct, so that "fresh" air comes in under the apartment door and then is exhausted through the bathroom. I have always thought it was a terrible system, because the air is being almost filtered through the dirty carpet at the apartment door, and you have no idea what is actually being pumped down from the roof or dragged through the corridor.

But a recently tweeted report from James Montgomery of the University of British Columbia and Lorne Ricketts of RDH Building Science shows that it is, in fact, even worse than I thought. The problem is that it is really hard to get balanced distribution of air; the top floors apparently get a lot more fresh air and have significantly better air quality.

Many of the lower floors have CO2 levels that exceed ASHRAE design guidelines. Lower floors also have higher humidity, leading to greater condensation on windows and mold. RDH concludes:

Air quality issues are common in many buildings and may lead to detrimental health effects among occupants.... The air quality issues were linked to poor ventilation air distribution within the building. The results at this case study building are likely representative of conditions of many low to high-rise multi- unit residential buildings ventilated with pressurized corridor systems.

The authors also recommend that other pollutants be measured, including carbon monoxide, ozone and, our bête noir, particulate matter, where there isn't even a standard.

PM2.5 is generated both indoors and outdoors by many sources such as household chores, cooking, and vehicle exhaust. Exposure to elevated levels of PM2.5 is associated with increased risk of cardiovascular and respiratory health impacts. There is no recognized lower exposure limit for PM2.5 and levels should be maintained as low as possible.

RDH Building Science

In the end, Montgomery and Ricketts recommend "replacement of a pressurized corridor system with new suite-level dedicated ventilation", like what one sees in Passivhaus buildings, with heat recovery ventilators in every apartment and apartment doors that are sealed and gasketted to keep out noise and corridor air. "Other potential methods to improve air quality include prevention of local outdoor sources, such as idling vehicles near ventilation intake, removal of indoor sources by using localized exhaust over cooking sources, or active removal of particles using an air filtration system."

People in apartments deserve better than what they are getting now, air pushed under their apartment doors with all the yucky dust, poop and pollen that comes with it. Everybody deserves fresh clean air.