Mygydau hidlo wedi'u cyfyngu gan yr amgylchedd

The use of filter-type respiratory protective equipment must be limited by the environment. When there are harmful substances in the environment that cannot be filtered by the filter material, or the oxygen content is less than 18%, or the concentration of toxic and hazardous substances is high (>1 y cant), Wrth ei ddefnyddio, dylid defnyddio offer amddiffynnol anadlol ynysig yn yr amgylchedd hwn.