The so-called spit guards will be used by all Metropolitan Police units in cases of police custody across London as a pilot scheme starting next month.
The devices, which are designed as mesh masks, will not be used on the streets as they are considered a "use of force".
"A pilot scheme has been approved for the use of 'spit guards' in all 32 MPS custody units from October 2016. These guards will only be used in a custody situation," a Met Police spokesperson said.
No decision has been taken over whether the "spit guards" will be used outside custody if the trial is successful.
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Research by The Guardian found that a minority of forces in England and Wales - nine of the 35 that responded to a Freedom of Information request by the newspaper - use the hoods.
UK's Police Federation has backed the move, arguing that spitting leaves officers at risk of contracting hepatitis.
"I'd rather take a punch to the face than be spat at. We do not deal with the most savoury people. Hepatitis is prevalent within the drug abuse community. I don't see it as a use of force, it is a health and safety issue," said Che Donald, the federation's health and safety lead.
However, human rights groups have expressed their concern over the move.
"A spit hood is a primitive, cruel and degrading tool that inspires fear and anguish. We have seen many cases where the police use them unnecessarily and without justification, including on children and disabled people," said a spokesperson for human rights group Liberty.
Amnesty International added: "Spit hoods can restrict breathing, create disorientation and can be dangerous and extremely distressing... Serious questions must be asked as to whether these restraints which have been criticised for breaching human rights guidelines should actually have a role in modern British policing.