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Recently, the houses next to us were fumigated with "Vikane", which apparently is $\ce{SO2F2}$. To my surprise, the gas was just pumped out in the atmosphere without further ado at the end of the procedure. I was told by the pest control people that this gas is "degraded by light" and that there is no hazard whatsoever for humans living close to the house. However, I've also read that sulfuryl fluoride is a potent greenhouse gas staying in the atmosphere for up to 40 years which it probably wouldn't do if it were deteriorated easily by light. Which is it??

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I think this pretty much comes down to three things:
1) The estimates of the atmospheric half-life of $\ce{SO2F2}$ has changed over time.
2) The current estimate of 30-40 years isn't a particularly long time relative to some other players (i.e. methane's atmospheric lifetime is around 6-8 years and that of carbon dioxide is around 50 years, though there is poor agreement on that one).
3) The emissions relative to the other greenhouse gas players is small enough to offset the fact that it is "potent" in this aspect.

From the sulfuryl fluoride Wikipedia page:

Based on the first high frequency, high precision, in situ atmospheric and archived air measurements, sulfuryl fluoride has an atmospheric lifetime of 30–40 years, much longer than the 5 years earlier estimated.

That addresses my first item. From the same page regarding my second and third items:

Sulfuryl fluoride has been reported to be a greenhouse gas which is about 4000-5000 times more efficient in trapping infrared radiation (per kg) than carbon dioxide (per kg). It is important to note, however, that amounts of sulfuryl fluoride released into the atmosphere (about 2000 metric tons per yr) are far lower than the amounts of $\ce{CO2}$ released by hydrocarbon-burning vehicles, industry, and other processes (about 30 billion metric tons per year).

That means that annual carbon dioxide emissions will trap 3000 times as much heat as will sulfuryl fluoride. So the pest control people may not have worded it quite right, but the bottom line is that sulfuryl fluoride emissions have a negligible effect on the planet's heat budget.

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