I made a really stupid mistake as a kid 28 years ago and spilled about one teaspoon of mercury onto a carpeted floor of a room about 12x12 feet. I’m assuming it was organic mercury only because it was taken from a junior high school science department and I’ve read that in this context it is typically organic mercury.

Is it likely there still could be mercury in the house at toxic levels after 28 years?

People still live in the house and I would like to get the air tested, however if it would have evaporated by now I would prefer not to worry people unnecessarily. My understanding is that there is no way to do this sort of test discreetly myself.

I lived in the room for 4 years after the spill and there was very little ventilation, the door was always closed so the only air coming in was from one air conditioning vent. During that time it probably was vacuumed a few times. After 4 years I moved out and for the past 24 years the room has had the door open and the air from the vent coming in. At one point the carpet was replaced.

I feel really terrible that I probably have caused my family harm. Later in life when I learned of the harmful effects, I told my dad about it who was a chemistry major and a medical doctor. This was about 20 years ago and he told me not to worry about it then. I assume that he must have had it checked and dealt with (later they changed the carpet) but I didn’t get a chance to ask him about it and confirm this before he died last year.

Now it is gnawing at me and I would like to get it tested but if it is safe by now, I’d rather not make everyone worry. They are very anxiety prone people and I don’t want them to worry the rest of their lives that they may have some long term subtle effects from that past exposure, considering there’s nothing that can be done about that past exposure now.

Thanks for any advice.

  • $\begingroup$ So, was it metallic mercury or organic mercury ? There is huge difference. What particular compound if not the metal? $\endgroup$
    – Poutnik
    Commented Aug 17, 2023 at 12:27
  • $\begingroup$ I don't know what you mean by "organic mercury". If what you spilled was a silvery, metallic liquid, it was NOT "organic mercury" but rather inorganic mercury. Metallic mercury is less toxic than mercury salts. And more likely to evaporate. $\endgroup$
    – Curt F.
    Commented Aug 17, 2023 at 12:27

1 Answer 1


According to a paper about dental amalgam and mercury exposure:

The evaporation rate of elemental mercury at room temperature (20 °C) is approximately 50 μg/cm²/h (range of 40–60 μg/cm²/hr).

If your teaspoon of mercury was about 5 mL in volume, and if it was metallic mercury, it would have amounted to about 67 g, based on mercury's density of 13.5 g/mL.

We need to know the surface area of the mercury to use the figure for the evaporation rate. In all probability, the surface area likely became very very large after the mercury was divided into many small droplets after it was spilled on the carpet.

But let's say the surface area remained very, very low, about 5 cm² only. That means about 250 μg, or about 0.25 mg, of mercury would evaporate each hour. And therefore the 67 g, or 67,000 mg, of mercury would evaporate in 268,000 hours, or about 30 years.

But a surface area of 5 cm² seems very low. If the mercury did not stay coalesced in one giant droplet, it was probably much higher than this, meaning the mercury is probably gone.

However, at these very long time scales, mercury may also oxidize to salts and other non-metallic forms of mercury, which would have effectively zero volatility. So it's probably a safe bet that a large fraction of the mercury you spilled is evaporated, with a smaller fraction that is still contaminating the carpet, not evaporating, perhaps removed by vacuuming, but perhaps with some low level of detectable mercury still there.

Only testing the carpet for mercury would say for sure, I guess.

  • $\begingroup$ Just a question. Do you remember the beginning of the problem ? Was it metallic mercury, which is a bright liquid often present in small droplets? Or was it a powder ? Mercury compounds like chloride, sulfate, or organic compounds (mercurochrome) are in general powders, like salt, sugar or talk powders. These powders will not get evaporated. So their vapors do not exist and are not toxic. $\endgroup$
    – Maurice
    Commented Aug 17, 2023 at 18:43
  • 1
    $\begingroup$ According to Curt F. 5 hours ago, a droplet of metallic mercury about 5 mL in volume would be evaporated in 30 years. This happens if no chemistry, no oxidation for example, is occurring during this time. If such a chemical reaction happens, the metallic mercury will be transformed into a new stuff, which is probably less volatil. So the carpet does not produce any toxic vapor any more today. And if the new stuff is more volatil than metallic mercury, mercury has already disappeared a long time ago from the carpet. $\endgroup$
    – Maurice
    Commented Aug 17, 2023 at 18:53

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