Ventilation Systems for Confined Space Manure Storage

Ag Safety and Health December 14, 2017 Print Friendly and PDF

Pig Barn with Slotted Floor

(Source: Agricultural Safety and Health, Pennsylvania State University)


Use the following format to cite this article:

Ventilation systems for confined space manure storage. (2013). Farm and Ranch eXtension in Safety and Health (FReSH) Community of Practice. Retrieved from


Ventilation is crucial in reducing risk exposure when entering a confined space manure storage. A manure storage is considered a confined space based on the criteria established by the Occupational Safety and Health Administration (OSHA). OSHA defines a confined space as 1) being a large enough space and configured in such a way that an employee can bodily enter and perform assigned work; 2) having limited or restricted means for entry or exit; and 3) not designed for continuous employee occupancy.

The following hazards exist in a confined space manure storage:

  1. Lack of oxygen,
  2. Toxic and flammable gases, and
  3. Potential exposure to drowning.

Ventilation Recommendations

The four main types of gases that can be in a manure storage area include hydrogen sulfide, ammonia, methane, and carbon dioxide. Ventilation of the area is recommended to decrease the level of these gases and to replenish the oxygen level in the manure storage.

Ventilation recommendations are based on the ANSI/ASABE S607 standard that was approved in October 2010 by the American Society of Agricultural and Biological Engineers. This standard was developed to reduce risk from asphyxiation, poisoning, and explosions prior to entering a confined space manure storage by specifying the positive pressure, forced ventilation requirements for the manure storage.

The type of flooring that is selected is based on the construction details of the facility and the type of animals being housed. Flooring type affects the type and design of ventilation systems to maximize air movement. The three main types of manure storage flooring and covers are solid, totally slotted, and partially slotted. A solid cover storage can be located beneath or outside the animal housing facility and may have a square, rectangular, or circular footprint. Rectangular and square storage footprints are typically used for partially and totally slotted floors that are located directly below the animal’s living area.

When a manure storage is being ventilated at an air exchange rate of 1.5 AC/m, the ANSI/ASABE S607 standard provides calculated times required to reduce hazardous gases to an acceptable level and to replenish the oxygen level from 0% to 20% within each type of manure storage tank. The standard also provides transformation equations or adjustment factors for alternative ventilation strategies, changes in AC rate, initial gas concentration levels lower than maximum documented levels, and differing fresh air intake locations. Click here for detailed information about calculated ventilation times, adjustments to calculated ventilation times, and information concerning the evacuation of animals from slotted-cover manure pits prior to ventilation.


The ANSI/ASABE S607 standard was designed to reduce the risk of entry into manure storages. In addition to recommended ventilation procedures, agricultural producers and workers should follow these recommendations:

  • Properly post warning signs near the entrance to confined space manure storage facilities.
  • Maintain ventilation instructions near the confined space manure storage for easy access in an emergency situation.
  • Never work by yourself when entering a storage. A second person who does not enter the confined space is needed.
  • Always monitor the gas levels in the storage before and during the entry event.
  • Ventilate the storage for the rate and time outlined in ANSI/ASABE S607 before and during the entry event.
  • Always use a safety harness and emergency retrieval system when entering a confined space manure storage.


To better understand strategies for reducing entry risks, view the following videos from the Pennsylvania State University:

Reducing Risk When Entering a Confined Space Manure Storage

Manure Storage Ventilation Demonstration: Slotted Floor Storage

Manure Storage Ventilation Demonstration: Solid Covered Storage


Click HERE to visit the Manure Pit Safety page by the Pennsylvania State University for additional information including fact sheets, manure pit standards and regulations, and the manure pit safety demonstration trailer.

Click on an article title below to be directed to an article from the Farm & Ranch eXtension in Safety and Health (FReSH) Community of Practice:

Confined Spaces Manure Storage Emergencies

Confined Spaces Manure Storage Hazards

Confined Spaces Manure Gas Monitoring



Use the following format to cite this article:

Ventilation systems for confined space manure storage. (2013). Farm and Ranch eXtension in Safety and Health (FReSH) Community of Practice. Retrieved from




Manbeck, H., Murphy, D., & Steel, J. (2011) Confined space manure storage ventilation systems. Pennsylvania State University. Retrieved from


Reviewed and Summarized by:
Linda M. Fetzer, Pennsylvania State University –
Dennis J. Murphy, Pennsylvania State University (Has since retired)
J. Samuel Steel, Pennsylvania State University (Has since retired)
Aaron M. Yoder, University of Nebraska Medical Center -

Connect with us

  • Twitter
  • Facebook
  • YouTube


This is where you can find research-based information from America's land-grant universities enabled by



SAY Project and National Clearinghouse

Women in Agriculture

Mobile Apps

Recursos en Español sobre Seguridad y Salud Agrícola

Resources Available

Education and Outreach

Self-Paced Learning

Instructor Led Learning

Training and Resources for Instructors


Upcoming Events

Video Resources

Articles (by Topic Area)


This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.