Social media has been flooded with apocalyptic scenarios involving a massive explosion at the Moscow refinery — one that could devastate the surrounding residential neighborhoods, or even the entire city. These posts frequently cite the views of Valery Legasov, the renowned Soviet chemist who led the Chernobyl disaster response.

Journalist Oleg Kashin shared a newspaper clipping in which scientist Vyacheslav Kazennov was quoted as saying:

Academician Legasov once calculated that a facility like this, built to a standard design, could produce an explosion more powerful than an atomic bomb. In principle, after a cataclysm of that scale, little would remain of the city.

Journalist Sergei Erzhenkov also cited a similar statement attributed to Legasov. We also found an article about Legasov by nuclear physicist Lev Feoktistov, who wrote:

Facilities like the one in Kapotnya near Moscow, or other large enterprises of the same type, contain millions of tons of flammable materials, while worldwide turnover amounts to around 10 billion tons of standard fuel equivalent — which in terms of energy density exceeds the combined yield of all atomic bombs. V.A. Legasov pointed this out on numerous occasions.

Despite these alarming quotes, there is no reason to expect an “explosion more powerful than a nuclear bomb.” Fuel storage facilities contain flammable — not explosive — materials, so an entire refinery cannot “blow up” all at once.

The drone strikes have nonetheless set off fires at the plant that are proving difficult to extinguish. This is a problem now facing Moscow and the surrounding region — one familiar to residents of Tuapse, Perm, and other Russian cities where drones have struck oil-industry facilities and caused severe air pollution from combustion byproducts.

Polluted air — whatever its source — is dangerous. And that is before even considering that combustion byproducts can contaminate drinking water.

When air is heavily polluted — even for just a few days — it leads to increased mortality, particularly among people with cardiovascular or respiratory conditions.

For most people, however, polluted air primarily causes short-term discomfort: irritated eyes, nose, and throat. Headaches and other health issues are also possible.

More serious harm becomes likely if the refinery burns for an extended period. In Tuapse, for example, a series of strikes on the local oil-processing infrastructure triggered a fire that took many days to extinguish, and Russia’s consumer protection watchdog, Rospotrebnadzor, detected elevated benzene concentrations in the air. Benzene is a known carcinogen — though current evidence links it to cancer only through chronic exposure. There is no agreed definition of chronic exposure, but even a fire lasting several days would not count as chronic exposure. At Kapotnya, then, much depends on how long combustion byproducts linger in the air.

Their best recourse is to leave the city temporarily.

If that is not an option and the local air is polluted with combustion byproducts, staying indoors with windows closed is the next best choice.

Anyone who needs to go outside should wear an FFP2 respirator (which may be sold under the N95 or KN95 label). Keeping a pack in an emergency go-bag is wise — but those without one can buy some at a pharmacy or through an online marketplace with fast delivery to the nearest pickup point. Protecting the eyes is also important: tight-fitting protective goggles are best, or at minimum ordinary glasses. Strenuous outdoor activity should also be avoided — exercising outside is a particularly bad idea.

On the morning of June 18, wind is carrying a cloud of combustion byproducts from the Kapotnya refinery fire farther to the northeast. Oil-contaminated rain has already fallen in the Moscow-region cities of Lyubertsy and Balashikha. As of publication, the fire is still burning.