Increase ventilation by simply opening windows and doors (fire doors should not be left open unless connected to a device that causes them to self-close upon activation of the fire alarm).
Dylech gynyddu'r lefelau awyru drwy agor ffenestri a drysau (ni ddylid cadw drysau tân ar agor oni fyddant wedi'u cysylltu â dyfais sy'n achosi iddynt gau eu hunain pan gaiff larwm tân ei seinio).