HOUSING
PIH-84
pork industry handbook
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA
Troubleshooting Mechanical Ventilation Systems
Authors
Richard E. Phillips, University of Missouri
William G. Bickert, Michigan State University
Reviewers
John Hamilton, Clayton, Delaware
Joe Bata, Adams, North Dakota
Development and use of mechanical ventilation in swine buildings has resulted in better environment and greater production efficiency. But when a ventilation system fails, problems occur which are easily recognized but often hard to solve.

This guide lists symptoms of several common types of system failure and likely causes. Nearly all of the problems described can be diagnosed by visual observation or with one of several simple tools.

A properly designed and operating livestock ventilation system provides an environment which is desirable for livestock—not people. Farm workers unfamiliar with a properly operating system will often report the building is too cold or the fans are moving too much air. But, in fact, the system may be operating as designed and creating the optimum environment for animal growth. Table 1 presents optimum temperatures and allowable ranges for swine. Information on ventilation rates can be found in PIH-60, “Mechanical Ventilation of Swine Buildings.”
Troubleshooting Tools
Several simple tools can greatly aid in system diagnosis. Most can be obtained at relatively low cost from suppliers of ventilation equipment or local heating contractors.

Thermometer
Ventilation systems rely mainly on temperature sensing devices to control air exchange rates. A good thermometer is essential to checking actual conditions and calibrating thermostats which control fans. Thermostats should be calibrated at least twice a year. Thermostat “range” (points at which they turn on and off) should also be checked at the same time.

Sling Psychrometer
A sling psychrometer consists of 2 thermometers suspended on a chain or sling. The sensing bulb on one thermometer is covered with an absorbent sock which is dipped in water prior to using (Figure 1). The two thermometers are then whirled on a sling in the area being investigated. The two thermometers produce readings known as “wet bulb” and “dry bulb” temperatures. These are used in conjunction with a chart furnished with the psychrometer to give relative humidity.

Winter time relative humidity within mechanically ventilated buildings should be 50-75%. Humidities above 80% will result in excessive moisture condensation on building or equipment components. They may also increase the incidence of disease.

Smoke Generator
Devices which produce dense smoke are used to “see” air patterns within a building. A bee smoker is suitable.
Smokers are useful in locating dead spots or drafty locations within a building.
Table 1. Temperature optimums and ranges for housed swine.
	Temperature (degrees F)	at animal level
Animal	Optimum	Desirable limits
Lactating sow	60	50-70
Litter-newborn	95	90-100
Litter 3 weeks old	80	75-85
Pre-nursery (12-30#)	80	75-85
Nursery (30-50#)	75	70-80
Nursery (50-75#)	65	60-70
Growing-finishing	60	50-70
Gestating sows	60	50-70
Boars	60	50-70