Firefighters are warning of the additional health risk fire smoke can pose on people with asthma and respiratory problems during the coronavirus outbreak.
The warning came after crews were called to a fire near Dinham Road near Caldicot, Monmouthshire, at around 11.25am on Wednesday.
In a social media plea, South Wales Fire and Rescue said: "Fire smoke can irritate airways. This may cause people with asthma and respiratory conditions to become unwell, as well as the risk from coronavirus.
"Please don’t make things worse for them, the NHS, or emergency services by starting a fire like this one in Caldicot yesterday."
The fire service said crews have been called to 36 grass fires in seven days, 30 of which were believed to be deliberate.
Emergency services across Wales have asked people to stay at home during the lockdown, which was announced by the Prime Minister on Monday.
Boris Johnson introduced strict new measures in the fight against coronavirus, in which people must stay at home unless they are carrying out essential activities such as shopping for food, exercising or going to work.
Police forces have been stopping cars to ensure people are adhering to the new rules.
South Wales Police have been patrolling coastal areas popular for days out and exercise activities.
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