How long does it take for VOCs to dissipate?

By Ian Cull, PE a.k.a. Indoor Air Nerd

About IndoorAirNerd: I’m I.A.N. the Indoor Air Nerd. To learn more about me, visit http://indoorairnerd.com/about

Contrary to what many may believe, it is quite difficult to predict how long it takes volatile organic compounds (VOCs) to off-gas from new materials in a specific building. Sure, you can do chamber studies under controlled conditions to determine emission or concentration decays, but how the material will behave in the real world can be quite different.

On Friday I was hired to perform a follow-up assessment for a home under construction that is experiencing elevated VOCs from varnishes and paints applied almost 7 months ago. One month ago I was in the home and found some very high levels based on measurements with a photoionization detector (PID). While PIDs are not as accurate or detailed as other methods of measuring VOCs, they can be used as a good screening tool with immediate feedback. I’ll write a blog post on the advantages and disadvantages of PIDs in the near future.

During my follow up visit a month later, I saw a 40% reduction after he followed some of my recommendations listed in this blog post: Reducing VOCs. Unfortunately, this was still 4 times the outdoor levels. We opened up some windows in a room and very quickly we saw a significant reduction. Here are a list of the problems:

* The home uses 2×6 “advanced framing” making the walls better insulated and tighter. However, the home is not bringing in mechanical ventilation. Many states have laws requiring mechanical ventilation.
* The owner selected hardwood floor varnish and oil-based paints high in VOC content and emission. He should have used products listed in the GREENGUARD Environmental Institute Product Guide.
* The owner moved in before the home was complete. It would have been better to wait for the VOCs to dissipate more.

So back to the question at hand… how long does it take? We can find some answers in a recent article in the Indoor Air Jounal titled “Decreasing concentrations of volatile organic compounds (VOC) emitted following home renovations”. The authors found a return to “normal” VOC levels after 2-3 months. The research was based on “real life” studies in Germany, not chamber tests.

Use the 2-3 month timeframe only as a guide, as my experience in the tight home with strong sources indicates it can take much longer.