Stopping Dirty Air May Stymie PRRS

Preliminary results using cleaning technology in barns show promise.

November 15, 2013

9 Min Read
Stopping Dirty Air May Stymie PRRS
<p>Minnesota swine veterinarian Gil Patterson displays a cyclonic air collector used to test air samples to test for the porcine reproductive and respiratory syndrome (PRRS) virus.&nbsp;</p>

Minnesota swine veterinarian Gil Patterson looks for three things when he walks into a hog barn: feed, water and air quality.

“You’ve got to have those things right before you can really dig into other issues. If there is a dusty, poorly ventilated environment, then it is uncomfortable for both pigs and farm employees, often leading to reduced growth and poorer-quality chores,” says the St. Peter, MN, Swine Vet Center clinician.

Stopping dirty air is an especially big challenge when dealing with hog barn dust. “Face masks are uncomfortable, and unless you are very diligent, you are probably not going to wear them,” he says.

EPI Technology

Electrostatic particle ionization (EPI) technology has been around a long time, but got the attention of the swine industry about four years ago when Baumgartner Environics of Olivia, MN, obtained a patent on the process, Patterson says, and started marketing it under the name EPI Air (

Basically, the technology works by continuously emitting a high concentration of negatively charged ions into the airspace. The ions transfer their charge to airborne particles, which are then attracted to grounded surfaces like a magnet. Clumps of dust will literally “stick” to gates, feeders or floors held in place by the ion field, Patterson explains.

There are two major components of this system in a hog barn: the transformer or power unit, and the corona lines, which are pipes suspended above the pens that extend the length of the barn. The ions are dispersed into the air from corona points, small metallic projections evenly distributed along the length of the pipe.

The original version of EPI-1.0 featured a wire suspended high at ceiling level. “It created environmental problems in the barn because dust would collect around the lights — and you want to work in a well-lit workplace,” Patterson comments.

Recently, the company released EPI-2.0. Its major advantage is the ability to change the height of the steel pipe that emits the ions. “You can come to work in the barns and press a control switch that activates a winch to elevate the pipe to ceiling level, which allows you to get into the pens and do your chores. You can then lower it back down to just above the pig level in the pen when you leave the barn,” Patterson says. The advantage of the new design is that it brings the ion field closer to pig level, providing a higher concentration of air-cleansing ions in the space the pigs are breathing.


Keep the most in-depth pork production information available at your fingertips! Download our Blueprint app today.


Additionally, there is less buildup of dust around the lights in the barn because the ion field is more focused on the pigs’ airspace, Patterson says.

“The ionization creates a field like static electricity. It will make your hair stand on end if you stand under it and produce a tingle in your arm if you place it under there. If you were to accidentally touch the corona pipe while the system is on, you will get a shock similar to that of an electric fence,” he says.

The hog barn may actually appear dirtier when you walk through it because of all of the clumps of dust that have settled on surfaces.

“What you don’t realize is that if you were in a room that didn’t have EPI Air, all of those dust particles would be in the air. With this system, the pig doesn’t have to focus as much of its energy on cleaning out its lungs and battling dust; it can concentrate on growing and not potentially stimulating the immune system,” Patterson says.

Early Research Results

Research from a Murphy-Brown hog operation in Utah looked at the impact of EPI Air on nursery pig performance. The data compared the nursery performance of more than 44,000 weaned pigs, evenly distributed between barns either with EPI (treatment) or without (control). Data were collected over five nursery turns from 2009-2010.

Using an optical particle counter, a precisely calibrated instrument that measures the amount and size of dust particles in the air, there was 40%-60% reduction in levels of both large and small dust particles. Hydrogen sulfide gas levels were also reduced by 58.6%. Average daily gains jumped by 12.2% and pig mortality was reduced by 1.2% in the rooms outfitted with EPI Air. This information was extracted from a talk at the 2012 American Association of Swine Veterinarians (AASV) annual meeting.

PRRS Research Proposal

Impressed by the data from the Murphy-Brown trial, Patterson set out to try to determine the technology’s potential role in controlling transmission of porcine reproductive and respiratory syndrome (PRRS). He developed a research proposal seeking answers to these questions:

● What effect does EPI Air have on PRRS virus?

● Can it reduce the quantity and viability of PRRS in aerosols generated by infected pigs?

● Can it reduce the amount of PRRS exhausted from the environment?

At the 2013 annual meeting of the AASV, held in San Diego, CA, Patterson’s proposal was awarded one of the 2013 Advancement in PRRS Research awards, a $25,000 research grant provided by Boehringer Ingelheim Vetmedica Inc. (BIVI). University of Minnesota graduate student Carmen Alonso, DVM, helped Patterson design the research study and also helped to collect samples and analyze the data.

“If we can show that EPI reduces the amount of virus that is exhausted from the environment, then it may have potential for helping to control regional spread. That would be a big deal for neighbors, especially in hog-dense areas,” he explains.

Hog Farm Study

The PRRS study was conducted at two sites in southern Minnesota during the summer of 2013. This report covers preliminary results of a triple-wide, 3,000-head, wean-to-finish farm in south-central Minnesota built in 2012.

The barn had three identical rooms, each with 1,000 finishing spaces. The EPI Air system was set up in two of the rooms, while the third room did not have EPI and served as control. Pigs were sourced from a PRRS-positive sow farm determined to be infected with an identical strain of the virus.

Upon entry, the barn was double-stocked to just over 6,000 head (2,000/room). Half of the pigs were moved off-site 5-6 weeks post-arrival.

The 21-day-old weaned pigs were moved into the barn on six weaning days over a 12-day period. “The main thing I did differently was I filled these rooms simultaneously instead of filling one room at a time,” Patterson says. Each wean day, those pigs were unloaded into a holding pen before being split evenly among the three rooms. This process was repeated until the rooms were filled.

“The idea behind this was to evenly distribute the ages and disease status of the pigs between the rooms. I wanted the amount of PRRS shedding in each room to be equal,” he says. Random pigs were also tagged and blood-tested on arrival, and PRRS-negative pigs were blood-tested later to see if there was any difference between the treatment and control rooms in how fast they converted positive to PRRS. Cotton ropes were also hung in each barn weekly to help determine when PRRS shedding would be at its peak.

Two weeks after the last wean day, nearly 67% of the pools of samples that were negative on wean day had turned positive, Patterson points out. And 100% of the ropes that were hung turned positive. “At this point, I knew there was a lot of PRRS moving around the barn, which was exactly where I wanted to focus my air sampling,” he says.

To test air samples for PRRS, he set up six cyclonic air collectors (two/room) to run simultaneously for 30 minutes per test period inside the barn. The same procedure was used outside the barn directly in front of the pit fans to find out how much PRRS virus was being exhausted from each room, he says. Air sampling was done four times per day for 13 days.


A total of 32% of the air samples taken in the rooms with EPI Air tested positive for PRRS, compared to 42% of the air tested in the control room (no EPI Air). A total of 57% of the air samples taken outside the treatment rooms were positive for PRRS virus, vs. 64% of the air samples taken from the control-room exhaust. Despite this encouraging trend, the results from this portion of the study were not statistically significant. 

Pigs that were initially negative for PRRS tested positive at a very similar rate between the rooms. “This suggests that the primary means of spread of the PRRS virus, once it is in a barn full of pigs, is nose to nose and less by aerosol,” Patterson says.

“There was also a 31% reduction in dust levels. After this study, I cannot say for sure that EPI reduces the amount of PRRS in the air. However, there does appear to be a trend toward reduction, which tells me that further testing is needed to find out the answer,” he says.


Although the results so far do not appear to be statistically significant, there are indications that EPI Air may lower the amount of aerosolized PRRS virus. “The potential to reduce risk may help prevent spread of disease in hog-dense areas. It may be a useful tool to help keep negative barns negative and positive barns contained.

“As a pig vet, when I go out to a farm to battle PRRS, I will take all of the help that I can get,” Patterson says.

Final performance closeout numbers for the trial are still pending. There are plans for a repeat trial this fall with a new group of PRRS-positive pigs. “Some questions that remain unanswered are the effects that seasonal ventilation differences will have on air sampling, as well as potential differences in the viability of virus between rooms,” Patterson speculates.


Battling PRRS virus in young pigs is always a challenge, Patterson says, limiting the significance of the results using EPI Air compared to healthy pigs (the Utah example). “If you have healthy pigs, I think you can expect huge performance gains — but if you are battling PRRS, it is harder.”

And either way, there are benefits to be gained from a cleaner environment and a better working environment for employees, he says.  

You might also like:

Evaluating 'Air Cleaning' Technology

Big Producers Make up Pig Losses with Heavier Weights

PED Virus Complicates Margin Management




Subscribe to Our Newsletters
National Hog Farmer is the source for hog production, management and market news

You May Also Like