The department claims to have carried out research that shows that high humidity, temperatures and sunlight can kill the virus on both surfaces and in the air.
Bill Bryan, DHS Science and Technology Advisor, said: “Our most striking observation to date is the powerful effect that solar light appears to have in killing the virus on surfaces and in the air.
“We’ve seen a similar effect as well where increasing the temperature and humidity or both is generally less favourable to the virus.”
In the study, the researchers looked at the virus’ half-life – the time taken for it to reduce to half its amount – in different environments.
When the temperature was 21-24°C, the half-life was 18 hours, but when the humidity was increased to 80%, the half-life dropped to six hours.
Meanwhile, in the presence of sunlight, the half-life topped to just 1.5 minutes, according to the researchers.
While the findings were praised by US President Donald Trump, they have not been made publicly available, raising concerns about their validity.
Speaking on MSNBC, Dr Irwin Redlener, director of the National Center for Disaster Preparedness at Columbia University, said: “’Everything that this scientist talked about from Homeland Security was basically incoherent, nonsensical, not really supported by evidence and really quite contrary to a lot of things we do know.”
Meanwhile, the World Health Organisation has warned that sunlight does not prevent coronavirus.
It explained: “Exposing yourself to the sun or to temperatures higher than 25C degrees DOES NOT prevent the coronavirus disease.