Rescuers are checking apartments in Narva.
They are looking for gas leaks.
Gas is dangerous.
People feel unwell.
Gas is invisible.
The smell of gas is bad.
It's hot in the apartments.
Ventilation doesn't work well.
Gas valves are being closed.
Windows are opened.
Gas appliances must not be used.
Ambulances take people to the hospital.
The gas detector shows gas.
Gas is deadly.