Screening ventilation strategies for confined-space manure storage facilities

Area of Science:

• Agricultural Safety and Health
• Environmental Engineering
• Occupational Health

Background:

• On-farm confined-space manure storage facilities pose annual risks of fatalities due to toxic gases like hydrogen sulfide (H2S).
• Asphyxiation and poisoning from methane, carbon dioxide, and H2S necessitate effective safety measures for confined space entry.
• Forced ventilation is a proven method to mitigate hazardous gas concentrations, making entry safer.

Purpose of the Study:

• To investigate the effectiveness of forced-air ventilation strategies in reducing toxic gas concentrations in confined-space manure storage.
• To identify ventilation methods that lower hydrogen sulfide (H2S) levels to the OSHA permissible exposure limit (PEL) of 10 ppm.
• To establish H2S concentration reduction curves and identify optimal ventilation for different manure tank cover types.

Main Methods:

• Experimental testing of forced-air ventilation strategies in a rectangular confined-space manure tank.
• Utilized hydrogen sulfide (H2S) as an indicator gas to monitor gas concentration reduction.
• Evaluated ventilation effectiveness under conditions simulating solid, fully slotted, and partially slotted covers.

Main Results:

• Identified typical H2S concentration reduction curves during forced-air ventilation.
• Determined promising ventilation strategies for reducing H2S to safe levels (OSHA PEL) and below 25% of initial concentration.
• Developed a field-based database for validating computational fluid dynamics (CFD) modeling protocols.

Conclusions:

• Forced-air ventilation is effective in mitigating hazardous atmospheres in manure storage tanks.
• Specific ventilation strategies were identified as most promising for different manure tank configurations.
• The generated database supports future CFD model validation for enhanced safety assessments.