How do I safely clean up rodent (rat, mouse or squirrel) urine and droppings in attic insulation?

Monday, June 25, 2018

After your observe the ugly evidence that rodents are living in the attic, your first step is to locate where they are getting in and close those entryways. Then trap them in the attic. The U.S. Centers for Disease Control (CDC) recommends to continue trapping for one week after the last capture. If no more rodents are found in traps after a week, and there is no evidence of further activity in the attic, then the infestation has been eliminated. More importantly, enough time has passed so that any virus in the rodent urine, droppings, and nesting material is no longer actively infectious.

    Before starting the clean-up of the attic, ventilate the area for at least 30 minutes. Try to use cross-ventilation during the airing-out period, if possible. 

    We suggest using a UV-flashlight with special yellow glasses, like the one shown at right, to make sure you catch all the areas of urine stains. Urine spots will light up (fluoresce) as purple under the ultra-violet light. The combination of flashlight and glasses normally sells for less than $15 online at Amazon or similar sites. Although it is only necessary to remove the contaminated areas of insulation, the UV-light may indicate that most or all of the insulation needs to be taken out if there has been a long-term infestation. 

    Here’s what the CDC specifically recommends:

  •  Wear rubber, latex, or vinyl gloves when cleaning up urine, droppings, or nesting materials. Note that a dust mask may provide some protection against dust, molds, and insulation fibers, but does not protect against viruses.
  • Spray any urine, droppings, and nesting materials with either a bleach and water solution (1 parts bleach to 9 parts water) or a household disinfectant prepared according to the label instructions for dilution and disinfection time. Soak well to inactivate any possible residual virus. Use a paper towel or rag to pick up the materials and dispose of them.
  • Any exposed insulation that has become contaminated with urine and droppings should be placed into plastic bags for removal.
  • Afterwards, decontaminate gloves with disinfectant or bleach and water solution. Wash hands well with soap and warm water.

    If you see evidence that rodents have also gotten into the heating and air conditioning ducts, the CDC recommends that you do not try to clean it up yourself. Contact a professional rodent exterminator. Companies specializing in duct cleaning are familiar with the problems and risks associated with rodent infestation in a ventilation system.

    Also, see our blog post How do I safely remove a dead rodent (rat, mouse or squirrel) from the attic?

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Here’s links to a collection of our blog posts about ATTICS:

What are the mistakes to avoid when doing attic improvements? 

What are the hazards to avoid when going into an attic? 

What is the most common type of roof-to-wall attachment? What are the building code requirements for installing an appliance (furnace, air handler, water heater) in the attic?

How do I safely remove a dead rodent (rat, mouse or squirrel) from the attic?

What are the common problems with attic insulation? 

Why is there no attic access hatch in the house?

How do I safely clean up rodent (rat, mouse or squirrel) urine or droppings the attic?

Why is there no attic access hatch in the house?

 Is an attic required to have a light by the building code? 

What is the building code requirement for an attic access hatch, scuttle, or door?

Why is vermiculite attic insulation a problem for both buyers and sellers of a home? 

What are the code requirements for NM-cable (nonmetallic-sheathed cable or Romex®) in an attic? 

What are the warning signs of a dangerous attic pull-down ladder?

Do home inspectors go on the roof? Do they get in the attic?

How much of a roof truss can I cut out to make a storage platform in the attic? 

• When was a fire separation in the attic first required between sides of a duplex? 

    Visit our ROOF AND ATTIC and SAFETY pages for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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