Type C Supplied-Air Respirators, more commonly

referred to as air-line respirators, are designed to

provide long-duration respiratory protection.

They generally consist of a full-facepiece or halfmask

facepiece connected by an air-supply hose to

an air source (either a compressor or bank of large

air cylinders). When connected to the air source,

the respirator delivers a supply of respirable air to

the user.

Accessory equipment, such as pressure regulators,

pressure relief valves, carbon monoxide monitors and

filters for air compressors, may be necessary to

ensure that the air is at the proper pressure and

quality for breathing. Air quality must be Quality

Verification Level Grade D or better as defined in

ANSI Standard Z-86.1-1973 (Compressed Gas

Association Specification G-7.1 Commodity

Specification for Air).

Current air-line systems fall into two categories:

between the two is how the air is supplied.

Pressure-demand systems deliver air only when the

user necessitates it. Thus, pressure-demand devices

afford greater breathing efficiency.

In contrast, with a constant flow device, air flow to

the respirator is continuous. However, because the

air flow is continuous, constant flow air-line systems

are generally used only with a compressor for a

virtually unlimited air supply.

Type C Supplied-Air Respirators are approved by the

National Institute for Occupational Safety and Health

(NIOSH) for use in atmospheres not immediately

dangerous to life and health (IDLH) or from which the

wearer can escape without wearing the respirator.

"Not immediately dangerous to life and health"

means any hazardous atmosphere which may

produce physical discomfort immediately, chronic

poisoning after repeated exposure, or acute adverse

physiological symptoms after prolonged exposure.

(42 CFR, Part 84 subpart A, 84.2(x)).

This limitation is necessary because the air-line

respirator depends entirely on an air supply not

carried by the wearer. Therefore, if the air hose were

severed or crimped, or the air compressor failed,

the air supply to the wearer would be shut off.

The wearer would be without respiratory protection

and might not be able to safely escape from an

IDLH atmosphere.

Another limitation of air-line respirators is that the

air-supply hose limits the wearer to a fixed distance

from the air source. As an air-line respirator user,

it is your responsibility to supply the respirator with

breathable air—Grade D or better. The following

pages show complete hook-ups of various air-line

systems, both pressure-demand and constant flow,

from the air source to the respirator. The following

information is a guide designed to aid you in hooking

up your own air-line system.

Pressure-Demand Air-Line Respirators are designed to maintain a slight positive pressure of air inside the facepiece whether the wearer is inhaling or exhaling. This helps prevent contaminants from seeping in around the facepiece, even if there should be small breaks in the face-to-facepiece seal. Pressure-Demand Air-Line Respirators are designed specifically for non-IDLH toxic atmospheres.

The exception is if the respirator is equipped with an egress cylinder of air to use during escape. Pressure-Demand Air-Line Units require an air supply from an uncontaminated compressed-air source as stipulated in General Industry Safety and Health Regulations, Part 1910.134 (OSHA) with the delivered air conforming to at least Grade D of ANSI Standard Z86.1.

A common air source for pressure-demand systems is a single cylinder of air which can be set up in remote sites that might otherwise be impossible to reach with a large stationary compressor. Another air source option for pressure-demand respirators is a cylinder cascade system. A cascade system consists of several air cylinders joined together in a bank by means of coupler tees. Generally, the banks consist of three cylinders of either 244 cubic-feet or 330 cubic-feetcapacity. One or more workers can breathe from a cascade system. If using a compressed air or a compressor system, each respirator requires 1.5 cfm per person and needs to maintain the inlet (working) pressure specified in the respirator instruction manual.

At a normal rate of consumption, a three-cylinder bank used with a pressure-demand unit will provide between 12 to 16.5 man-hours of air, depending  on cylinder capacity.

Constant Flow Air-Line Respirators also maintain a slight positive pressure of air inside the facepiece whether the wearer is inhaling or exhaling. This helps prevent contaminants from seeping in around the facepiece, even if there should be small breaks in the face-to- facepiece seal.

Constant Flow Air-Line Respirators maintain air flow at all times, rather than only on demand. Because of this, constant flow units almost always use a compressor as their air source. A constant flow unit would quickly exhaust the air from a cylinder or cascade system. There are two types of Constant Flow Air-Line Respirators: one uses a tight-fitting facepiece; the other, a loose-fitting hood or helmet. Inlet air pressure must be able to maintain at least

• with Escape Cylinder

(for egress from IDLH atmospheres)

• with Vortex Tube

(for suit-cooling applications)

• with Dual-Supply

(to eliminate additional hose lengths)

• with Duo-Twin Option (for a combination

air-supply/air purifying respirator)

(only approved with 1/4-turn regulator)

• with Duo-Twin Option (for a combination

air-supply/air purifying respirator)

(only approved with 1/4-turn regulator)

Pressure-Demand Air-Line Respirator

Pressure-Demand Duo-Twin™ Respirator

Pressure-Demand Duo-Flo™ Respirator

• Synergy® Bubble Hood Respirator

• Versa-Hood™ Air-Supplied Hood

• Constant Flow Air-Line Respirator

• Constant Flow Direct-Connect Air-Line Respirator

• Constant Flow Duo-Twin™ Air-Line Respirator

• Constant Flow Duo-Flo™ Air-Line Respirator