Some have speculated that deadly fungus could have grown in the enclosed tombs and been released when they were open to the air. Arthur Conan Doyle favored this idea, and speculated that the mold had been placed deliberately to punish grave robbers.
A newspaper report printed following Carnarvon’s death is also believed to have been responsible for the wording of the curse most frequently associated with Tutankhamun – “Death shall come on swift wings to him who disturbs the peace of the King” – a phrase which does not actually appear among the hieroglyphs in KV62, even though it was said to appear in several different places.
While there is no evidence that such pathogens killed Lord Carnarvon, there is no doubt that dangerous materials can accumulate in old tombs. Recent studies of newly opened ancient Egyptian tombs that had not been exposed to modern contaminants found pathogenic bacteria of the Staphylococcus and Pseudomonas genera, and the moulds Aspergillus niger and Aspergillus flavus. Additionally, newly opened tombs often become roosts for bats, and bat guano may harbour histoplasmosis. However, at the concentrations typically found, these pathogens are generally only dangerous to persons with weakened immune systems.
Air samples taken from inside an unopened sarcophagus through a drilled hole showed high levels of ammonia, formaldehyde and hydrogen sulfide; these gases are all toxic, but are easily detected by their strong odours. Hydrogen sulfide is detectable at low concentrations (Up to 100PPM) beyond which it acts as a nerve agent on the olfactory senses. At 1000ppm it will kill with a single inhalation. [19]