Effective Containment & Ventilation Systems, Easier Said Than Done

The rehabilitation and painting of industrial structures often requires the use of containment systems equipped with adequate ventilation systems as feasible engineering controls to reduce worker exposure and emissions. The design of containment systems and ventilation air flow rates seems easy enough, however, proper implementation of the design can become a problem. Some of the issues may stem from a structural engineer’s lack of field experience in ventilation, while other problems may arise when a contractor freelances to benefit their bottom line. In either instance, it is beneficial to owners, contractor employees and the general public that an experienced independent third-party representative check and verify the containment and ventilation is installed and performs as designed.

The benefits of having a fully functioning containment and ventilation system are key to completing a project safely and effectively. The following list highlights the benefits of the aforementioned engineering control :

• Protects the public and environment from hazardous material and abrasives migrating from the project site.
• Proper ventilation typically improves visibility, which can increase employee productivity.
• Reduces the likelihood of fugitive hazardous dust emissions escaping the containment area.
• Allows a contractor to quickly collect and recycle abrasives.
• Provides employees with better air movement and will assist in reducing exposure to airborne dust (coupled with the adequate PPE).
• Reduces the chance of overspray impacting the public during paint operations.
• Provides a more manageable work area for paint application and more efficient inspection.
• Enables the contractor to control ambient conditions through dehumidification or heating.

Recently, I have served in the role of a Competent Person (SSPC C-3) for the de-leading of industrial structures. I have encountered several problems that reduce the effectiveness of containment and ventilation systems. Some issues are caused by contractor lack of diligence, while some are caused by an act of nature. Some are just random unpreventable occurrences. However, these problems can be reduced or eliminated if cooperation between the contractor and inspection team exists. The following list provides an example of common containment and ventilation system issues:

• Dust collector unit running on idle or reduced RPM rather than at optimal RPM levels.
• Dust collector air ducts that have been damaged or improperly connected.
• Dust collector air ducts that are improperly attached to the dust collection unit or improperly inserted into the containment system.
• Dust collector air ducts with rigid 90-degree elbows increasing turbulence and reducing efficiency of the ventilation system.
• Improper location of air supply (Intake) points.
• Improper orientation of air supply (Intake) flaps.
• Containment joints that are not fully sealed.
• Holes, tears or rips in containment materials caused by outriggers, sky climbers, abrasives or high winds.
• Heavily soiled mechanical ventilation filters unable to capture the necessary dust and debris.
• Lack of fully sealed divider tarps which allow short circuiting of ventilation rather than as designed to reduce the size of individual containments.

A commonly referenced document in the surface preparation and painting of industrial structures industry is SSPC Guide 6 – Guide for Containing Surface Preparation Debris Generated During Paint Removal Operations. This document provides contractors, designers and owners with guidance in regards to design, construction and monitoring of ventilation and containment systems. Guide 6 discusses several different strategies in determining the effectiveness of a particular containment/ventilation system. The options below provide a framework to judge the effectiveness of the containment/ventilation system (some specified containment systems are less stringent than others).

• Visual verification of negative pressure on the containment structure. Containment should exhibit a concave posture to demonstrate negative pressure. Wind direction must be taken into account as that can provide a false positive when viewed from certain directions.
• Instrument verification using a manometer or magnehelic gage to ensure negative pressure throughout the enclosure.
• Visually inspect containment system to ensure all joints are adequately sealed without holes, rips or tears.
• Monitor the exterior of the containment during dust generating activities for any fugitive dust emissions.
• Conduct ambient air monitoring for toxic metals (TSP or PM-10).
• Perform occupational monitoring of regulated areas.

In conclusion, field verification of containment and ventilation systems is equally as important as the engineering and design of the aforementioned systems. Without adequate implementation and continuous verification in the field, the potential benefits of the containment and ventilation systems will not be realized. Failure to construct adequate containment and ventilation systems can result in damage to private property, hazardous material releases, elevated dust exposure for employees and the public, and reduced productivity. Due diligence, cooperation and daily inspection by all parties involved can ensure that your containment/ventilation system won’t be an issue on your next project.