FFP1 dust masks give the minimum level of protection against non-toxic particulates however this may be perfectly acceptable depending on the airborne hazard. As they are composed of the least amount of filter material they also provide the least breathing resistance and quite often an exhalation valve is not required.
FFP1 dust mask protection examples: brick dust, cellulose, cement, coal dust, gypsum, limestone, Plaster of Paris, pollen, sugar.