... installed. Rotate anticlockwise to remove the round cap on the top of the filter, then unclose the ... 103G.3. CautionsThis product is unsuitable to anoxic (i.e. oxygen content less than 18%) or explosive ... or valves are cracking, tearing or dirty, please do not use. If feel uncomfortable, high resistance or ... the working place and check the mask or change a new filter.After use, take out the filter ...