Factory performance evaluations of engineering controls for asphalt paving equipment

Area of Science:

• Occupational Health and Safety
• Industrial Hygiene
• Environmental Engineering

Background:

• The asphalt paving industry requires effective engineering controls to manage emissions.
• The National Asphalt Pavement Association (NAPA) partnered with the National Institute for Occupational Safety and Health (NIOSH) to address this need.
• Development and evaluation of prototype engineering controls were necessary to capture asphalt emissions.

Purpose of the Study:

• To develop and validate a novel analytical tool for assessing engineering controls in asphalt paving.
• To evaluate the performance of prototype engineering controls designed to capture asphalt emissions.
• To identify design limitations and optimize controls for improved capture efficiency.

Main Methods:

• A dual-method protocol combining qualitative smoke visualization and quantitative tracer gas (sulfur hexafluoride, SF6) testing was employed.
• Prototype engineering controls were tested under controlled indoor conditions using theatrical smoke and SF6.
• Outdoor evaluations assessed control performance under realistic environmental conditions, including wind gusts.

Main Results:

• Indoor evaluations showed prototype capture efficiencies ranging from 7% to 100%.
• Outdoor evaluations demonstrated a significant decrease in capture efficiency (down to 1%) due to wind interference.
• The tracer gas protocol successfully identified design flaws and highlighted the importance of enclosure design and ventilation rates.

Conclusions:

• The developed testing protocol is a valuable tool for evaluating and optimizing engineering controls for asphalt paving equipment.
• Effective engineering controls require a combination of good enclosure design and adequate exhaust ventilation.
• Stationary performance evaluations are crucial for identifying design strengths and weaknesses before costly field studies.