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We recently (a month ago) had our oak floors refinished with Precision Oil Modified Polyurethane. The odor has diminished substantially, and I hardly notice it at all any more, except sometimes when I first enter the house.

But my partner is worried about the toxicity and has the windows open and many fans on during much of the day. Until the other day, we thought that the finish was purely oil-based, but from other articles on this site, it appears that it mainly water-based -- which we thought we had been avoiding due to concerns about appearance and durability.

Is she right to be so worried about the toxicity? How long should we be subject to outgassing, and are fans the best way to speed up the process? (In a few weeks, it might not be so comfortable to keep the windows open.)

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  • Your experience isn't atypical. I'm not sure if any manufacturer is completely frank about this but there's a chance that some odour (which is somewhat equivalent to 'new car smell') can persist for quite some time. It does diminish over time naturally, but when a large area like the floors in a house are finished users should be prepared to still be able to notice it upon first entering the space not just for some days but a few weeks, or a month+ as in your case. [contd]
    – Graphus
    Sep 19, 2019 at 6:49
  • When just the walls in a room are repainted I've often been able to detect the characteristic smell of emulsion (what you call latex paint) well past a week later, sometimes into the third week. But eventually you come in and don't notice, then some time later you realise that you're not noticing it and wonder when it went away :-)
    – Graphus
    Sep 19, 2019 at 6:51

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The odour from waterbased finishes can sometimes be surprisingly strong and pervasive, but there's usually little cause for concern because the ingredients are relatively benign, and certainly the VOC load is just a fraction of that from an equivalent oil-based finish. But, what you're smelling in each case are completely different things.

Is she right to be so worried about the toxicity?

I'd say the answer to this is probably not, but there's no point in someone here speculating on what you're smelling in this case and the risk it may pose, contact the manufacturer and they'll be able to put your mind at rest.

How long should we be subject to outgassing

Impossible to say. In all finishing drying processes take as long as they take, depending on the exact product used (not just its type) and subject to the temp and humidity, the thickness of finish application etc.

and are fans the best way to speed up the process?

Yes. Good airflow is the number one thing that will help.

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Certainly, such products all contain VOCs and other interesting compounds, and most manufacturers will publish clear warnings about their use and potential health issues using and applying it.

Usually these warnings are specific to the application and drying times. In general, for many of these sorts of products, "drying" means 72 hours (depending on circumstances) for light use and 7 days (again, depending) for a more permanent cure. But see the application and safety notes published for your brand.

Actually, what is probably more of an issue is that the strength of the odour may not actually be indicative of a level of danger. The odour just reminds us that there may be some nasty stuff present. For all we know, some huge percentage of the worst compounds boil off in the first X hours or days, and the lingering odour is just some reasonably low-toxicity VOCs that we are sensitive to.

As Graphus says, you probably don't have much to worry about, though the manufacturer will publish warnings, and in this case I suspect the warnings will read something similar to this:

CAUTIONS: CONTAINS DIMENTHYLETHANOLAMINE AND 1-METHYL-2-PYRROLIDONE. CONTAINS MATERIAL THAT MAY CAUSE REPRODUCTIVE EFFECTS AND MAY ADVERSELY AFFECT THE DEVELOPING FETUS BASED ON ANIMAL DATA.

Etc.

Again, this is more about application and initial curing, and probably not the long tail of a full cure. It is also based on laboratory tests involving fetal rats and pigs, which doesn't always translate well for "humans walking around in a house, but also doing other things".

But reasonable caution suggests that you continue reasonable ventilation. You probably don't need to walk around with NIOSH approved breathing masks after the first few hours...

The problem is that it is hard to predict the affects of low level exposure of these compounds in humans after the initial bloom of application and curing. The fact is many of these finishes are perfectly safe when used as directed, but there is no denying the other fact that the compounds they release during cure are not something adult humans want a lot of during a lifetime. The manufacturers are actually not able to state that these products are "safe" (for some definition of "safe") after X hours or weeks, as safety is dependent on so many factors out of their (and your) control.

I, personally, might wait even a few weeks after application before introducing pets, small children, or pregnant women to such environments.

But this is more of a gut feeling rather than a quantifiable situation.

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