Poultry Houses and Ammonia: Pull Tubes and Diffusion Tubes

- [Instructor] Let's talk about using colorimetric or detector tubes to measure ammonia gas levels in poultry houses and other types of barns.

There are a few different types, but measurements are interpreted in similar ways and they offer reasonable accuracy compared to other measurement devices.

I'll demonstrate how to use them, then talk about advantages, disadvantages, and costs associated with each type of colorimetric tube.

These are colorimetric tubes.

The pen-sized glass tubes change color along their length after exposure to ammonia, as the contents of the tube react with the gas in the air.

The length of the color change on the detector tube indicates the concentration of ammonia, just like a glass thermometer indicates temperature.

The ammonia concentration is determined by reading a scale along the tube at a location where the color has stopped changing.

There are two main types of colorimetric tubes, pull tubes and diffusion tubes.

Pull tubes are a portable, quick, and relatively inexpensive way to detect ammonia gas levels.

Both ends of the glass tube are broken off.

Then the tube is inserted into a handheld sampler pump that costs between $400 and $700.

This manually operated piston-type pump draws an accurate volume of sample air through the colorimetric tube.

This offers a one-time spot check of ammonia level at a location of interest.

The pump draws air through the tube for several seconds.

It is very important to hold the pump such that the air pulled in through the tube comes from the location of interest.

For example, if animal welfare measurements are the goal, this means holding it near the bird breathing zone during the sampling period.

Several types of sampling pumps are available, but the pump and pull tubes must be from the same manufacturer to match the volume of ambient air drawn through the tube with the reaction rate of the tube contents.

As with other instruments, the pumps need to be periodically checked for problems such as leakage due to old and worn seals.

Your individual pump will have specific instructions to do this.

The thin glass colorimetric tubes are available for dozens of different types of gases.

The tube content is specifically reactive with the type of gas that is being measured, including those that may be found in farm animal environments, such as ammonia, hydrogen sulfide, and carbon dioxide.

Diffusion tubes, also known as passive tubes or dosimeter tubes, offer an even less expensive colorimetric option to monitor ammonia gas in the animal environment since a pump is not needed.

Diffusion tubes also provide an average ammonia level over a period of several hours, rather than the spot check of the pull tube, which can be an advantage.

Testing starts by breaking off one end of the diffusion tube and noting the deployment time written on the tube.

Then the tube is positioned in the environment of interest.

As the name implies, ambient air slowly diffuses into the tubes contents causing a change in color due to the chemical reaction with gas in the air.

A diffusion tube gathers information over two to 10 hours in concentration time units of PPM hour, or parts per million times hours.

A scale is provided on the side of the tube for the direct reading.

This concentration time reading is divided by the number of hours of exposure to the barn air, to get the average concentration in parts per million over that monitoring period.

The tube can be positioned near, but out of reach of the animals for animal welfare concerns, or at building ventilation exhaust outlets as part of an emission calculation.

One disadvantage of the diffusion tube process over pull tubes, is the need for two visits to the animal environment hours apart, to place the tube and to retrieve the concentration reading.

Pull tubes and diffusion tubes come in a choice of measurable ranges so that suitable analysis is possible.

They cost about $8 to $12 each and are sold in boxes of 10.

Tubes are available with different measurement scale ranges.

For example, from 2 to 30 parts per million, or from 5 to 100 parts per million.

The latter is recommended for most poultry houses, particularly those within house manure storages such as high rise layer or broiler houses with built up multiple cycle litter.

Within a poultry manure storage environment, ammonia monitoring is needed up to 500 parts per million.

Tubes should be stored in a cool, dry, and dark place, and need to be used prior to the expiration date indicated on the box.

Tubes have a typical shelf life of one year.

Colorimetric tubes are widely available, have a relatively low cost, and offer a reliable and proven method for roughly measuring ammonia gas concentrations in animal environments.

They can be used to take a quick snapshot of ammonia levels at various locations around the barn, and should be kept on hand for farmworker and animal safety.