|Priority Safety Services
"Your Safety Is Our Priority"
Principles of Operation
Inhaled air is drawn through either the air-line (when connected and air is flowing) or
through the respirator cartridge (when air is not flowing). The air is then drawn into the
facepiece (where it passes over the facepiece lens to minimize fogging) before it is taken
into the lungs. Exhaled air then leaves the facepiece through an exhalation valve.
Approvals & Standards
MSA Constant Flow Duo-Twin Respirators are approved by the National Institute for
Occupational Safety and Health (NIOSH) and the Mine Safety and Health Administration
(MSHA) for use in atmospheres not immediately dangerous to life and health.* These
respirators are approved with an inlet pressure range of 35 to 40 psig and with 8-300 ft.
of MSA Air-Supply Hose. The respirator requires a source of compressed air conforming
to at least Grade D (Compressed Gas Association, Inc., Commodity Specification for Air,
G-7.1, which is now ANSI Z86.1-1973).
Particulate and Dust
Toxic Atmosphere Non-IDLH
MSA offers Duo-Twin Air-Line respirators in both Constant-Flow and Pressure-Demand
versions. Constant-Flow respirators are normally used where there is an ample air supply
such as provided by an air compressor. Pressure-Demand respirators are generally used
where only compressed-air cylinders are available. MSA Duo-Twin respirators feature
air-purifying cartridges, which also protect against a variety of contaminants. If the air
supply should ever fail on the Constant-Flow unit, the user is automatically protected by
the air-purifying cartridge. This product is popular in the pharmaceutical, chemical,
petrochemical and nuclear industries. The unique Demand/Pressure-Demand (D/PD)
switchable exhalation valve, standard on Pressure-Demand models, also makes these
units especially well-suited for abatement work. This MSA respirator should not be used in
atmospheres containing less that 19.5% oxygen.