Mercury can kill you.
It is rare that immediate exposure to mercury is fatal. Serious health effects from mercury are more likely due to long-term exposure.
The mercury found in an old-fashioned thermometer is unlikely to cause death or even long-term health effects because it is “elemental mercury.” Elemental mercury is unlikely to kill someone even if it is ingested because gastrointestinal absorption is less than 0.01% of the dose. The average person is unlikely to die from immediate exposure to elemental mercury during their life. [“Toxicity of Mercury.” Journal of Human Hypertension]
Mercury compounds can and have killed people. Methyl mercury compounds are easily absorbed into the bloodstream; these are the kinds of mercury found in fish. It is usually long-term exposure to these kinds of mercury that harm humans, not short-term exposure. In cases of death through short-term exposure, there was usually a disaster involved, such as the Minimata tragedy or the deaths caused by improper fertilization of corn in Iran. [ToxFAQs™: Mercury.” ATSDR]
In its liquid form, mercury also releases vapors. However, sudden death by mercury vapors is a rare thing because the concentration of mercury vapors required to kill a person is very high and is usually found only in industrial areas. It is only in sealed, unventilated areas that mercury vapor could conceivably become a danger. Therefore, it is important to ventilate any room where liquid mercury has been exposed to the air. Chronic damage from long-term, low-level exposure is more common, and includes permanent damage to the brain and kidneys. Effects from these types of chronic damage is more likely to kill someone and not exposure to the fumes alone. [“Occupational Safety and Health Guideline for Mercury Vapor” OSHA]
“Toxicity of mercury.” Journal of Human Hypertension (1999) 13, 651–656. N.p., n.d. Web. 2 Jan. 2013. http://www.nature.com/jhh/journal/v13/n10/pdf/1000896a.pdf ( reference to minimata)
” ToxFAQs™: Mercury.” ATSDR Home. N.p., n.d. Web. 2 Jan. 2013. http://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=113&tid=24
“Occupational Safety and Health Guideline for Mercury Vapor.” Occupational Safety and Health Administration – Home. N.p., n.d. Web. 8 Jan. 2013. http://www.osha.gov/SLTC/healthguidelines/mercuryvapor/recognition.html