Skip to main Content

Could weatherization be harmful to human health?

  • Author: Craig Medred
  • Updated: September 27, 2016
  • Published September 27, 2012

Going for a walk might clear your head for chemical reasons you never imagined. A small, new study reported by the National Institutes of Health indicates that carbon dioxide accumulations in your office or home could be seriously muddling brain function.

Usha Satish at the State University of New York, Mark Mendell at the Lawrence Berkeley National Laboratory in California and colleagues report that CO2-heavy indoor air cuts human decision-making performances by 11 percent to 94 percent.

Their study, in the NIH magazine Environmental Health Perspectives, goes so far as to warn "direct adverse effects of CO2 on human performance may be economically important and may limit energy-saving reductions in outdoor air ventilation per person in buildings."

Carbon dioxide has been steadily accumulating in indoor air as more and more steps are taken to make buildings tighter to cut heating costs. Could it be slowing brain function?

Saving energy, harming health?

The state of Alaska funds an entire program aimed at weatherizing homes by making them more energy efficient, more air tight. The new study brings into question what such energy-saving efforts might be doing to the people inside. There are no standards for home CO2 levels, and the state does not require weatherization professionals to test for carbon dioxide levels, according to Curt Christiansen, housing manager for Alaska Housing Finance Corp.

The U.S. Occupational Safety and Health Administration recommends a maximum indoor concentration of 5,000 parts per million in the workplace.

Satish, Mendell and others found that carbon dioxide became a problem at levels far lower than the federal standard. Human performance began to fall at 600 ppm and decreased significantly by 2,500 ppm:

The substantial reductions in decision-making performance with two-and-a-half-hour exposures to 2,500 ppm indicate ... impairment that is of importance, even for individuals. These findings provide initial evidence for considering CO2 an indoor pollutant, not just a proxy for other pollutants that directly affect people.

Carbon dioxide is a natural, organic gas. All mammals expel it as a waste product when they breathe. Outside, CO2 quickly disperses into the atmosphere. Indoors, it is trapped. Thus indoor air invariably contains more CO2 than outdoor air, and humans can tolerate large concentrations. It takes concentrations greater than 250,000 ppm to kill you -- and generally more than 20,000 ppm to make you notice that you're breathing harder.

Head outdoors

Lower concentrations had not been thought to be a serious threat; indeed, Christiansen at AFHC said that carbon dioxide testing has not even been discussed within Alaska's industry of businesses that provide weatherization services. But the new findings raise questions about that -- as well as possibly shed some light on why you might find your thinking more clear-headed when you venture outside the office or home.

The study could prove troubling for Alaskans who spend large parts of the winter cooped up in energy-efficient homes and offices that hold increasingly higher concentrations of carbon dioxide. On the other hand, if you needed an excuse to get outside for a walk, hike, run or ski, this may suffice.

It might also be a good time to ask your office manager to invest in a few hearty plants that require little light or warmth. Plants absorb carbon dioxide and contribute oxygen to the atmosphere, which might make the office a little more tolerable come December.

Contact Craig Medred at craig(at)

For more newsletters click here

Local news matters.

Support independent, local journalism in Alaska.