Negative Pressure Enclosure

Negative Pressure Enclosure (NPE) systems may be used where the configuration of the work area does not make the erection of the enclosure infeasible, with the following specifications and work practices:

• The NPE may be of any configuration.
• At least 4 air changes per hour must be maintained in the NPE.
• A minimum of -0.02 column inches of water pressure differential, relative to outside pressure, must be maintained within the NPE as evidenced by manometric measurements.
• The NPE must be kept under negative pressure throughout the period of its use.
• Air movement must be directed away from employees performing asbestos work within the enclosure, and toward a HEPA filtration or a collection device.

The following working conditions must occur in a NPE:

• Before beginning work within the NPE and at the beginning of each shift, the enclosure must be inspected for breaches and smoke-tested for leaks, and any leaks sealed.
• Electrical circuits in the enclosure must be deactivated, unless equipped with ground-fault circuit interrupters.
• Glove bag systems may be used to remove presumed asbestos containing material and or asbestos containing material from straight runs of piping and elbows and other connections.

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