How you disinfect an outside pet area depends on the materials involved. If you're dealing with an outside dog run with concrete or similar flooring, the disinfection process is fairly similar to indoor kennels. If you're trying to disinfect an outside area with just dirt on the ground, that's a different story. You can't really disinfect soil, but you can use certain substances to kill viruses harmful to pets.
Using the right disinfectant means you'll kill off, or greatly reduce the number, of pathogens in the outside pet area. There isn't a one-size-fits-all disinfectant, so make sure you apply a solution that will eradicate a specific contaminant present in your pen, if that's your goal. One of the best general and most economical disinfectants is bleach. A mix of one part bleach and 30 parts water will kill even tough viruses such as parvo. Leave the bleach on the contact surface for at least 10 minutes before rinsing. Whatever disinfectant you choose, mix and apply it according to the manufacturer's directions.
When disinfecting an outdoor run, remember to remove all bowls, toys and other objects. Replace the bowls with clean ones, or use a mild disinfectant to clean them and let them air-dry. Remove any feces. Hose down the run with hot water. Apply your disinfectant of choice, preferably with a sprayer, over every area of the run. With a stiff brush, thoroughly scrub every inch. Follow the manufacturer's directions for the length of time the disinfectant must remain on the surfaces. When that time is up, spray hot water and completely rinse the run. Let the run air-dry or use a squeegee to speed the process.
Watering Grass Enclosures
While you can't truly disinfect grass, you can dilute the presence of any contaminants via watering -- if the pen has good drainage. If drainage is poor, don't use the watering method. You'll simply make a muddy mess. In areas with adequate drainage, after picking up and disposing of any fecal material, water the grassy area thoroughly. Another option for disinfecting grassy areas is spraying with accelerated -- not regular -- hydrogen peroxide. Potassium peroxymonosulfate, used to disinfect swimming pools, also can be sprayed on grassy pens to kill parvo and other viruses.
Sunlight is the Best Disinfectant
If your goal in sanitizing an outside pet area is to kill specific viruses, sunlight aids in disinfection whether or not you've applied commercial remedies. If you experienced parvo in an outside dog pen, for example, it can take at least five months for the pen to be safe for use if it gets plenty of sunlight. If the pen is partially or wholly in shade, it takes at least seven months for the virus to disappear. That time frame is without the use of disinfectants. If you're trying to eradicate other contagious diseases simply by sun exposure, ask your vet about the necessary time requirements.