Attic Rodent Cleanup and Sanitation

Purpose

Rodent droppings and urine dry into the insulation, and the only way to remove them is to disturb them. The hazard is not the material lying there, it is the aerosol a broom, a shop vacuum or a knee makes out of it. A tech who sweeps a contaminated attic puts more airborne material into their own breathing zone in ten minutes than the homeowner inhaled in a year of living under it.

So this SOP guarantees three things: nothing dry ever moves, the attic is cleared as a workspace before it is cleared as a contamination job, and the fill goes back to the depth it was at, measured.

Scope

Covers cleanup and sanitation of commensal rodent contamination in residential and small commercial attics: droppings, urine staining, nesting material, carcasses in the open, contaminated insulation, and the ectoparasites left after a die-off. Covers the entry gate for the attic itself.

Does not cover sealing the rodents out, owned by the rodent exclusion SOP, which has to be finished or booked before this runs. Bait placement is the rodent bait station SOP, wildlife species and their legal gates are the wildlife exclusion SOP, and crawlspace contamination is the crawlspace standard. A carcass inside a finished wall is a construction referral.

Roles and responsibilities

Procedure

Step 1 - Confirm the way in is closed and identify what you are cleaning. Read the exclusion ticket, confirm from the access that its entry points were sealed, and name the species from droppings, gnawing and nest material, since a deer mouse in a rural or semi-rural attic is the population associated with hantavirus in North America. Acceptance: exclusion signed off or booked with a date, species recorded, contaminated area sketched into numbered zones with a square foot figure on each. Wrong looks like a cleanup sold in an attic still open at three soffit returns; stop rule, exclusion neither complete nor booked and the cleanup does not run today. Hazard: none at this step, it is read at the hatch off paperwork, and the ladder stays down until step 2 sets it.

Step 2 - Gate the attic itself before you commit to it. Read dry-bulb temperature at the hatch and at the far end, look for knob and tube wiring, open splices and uncovered boxes, and lay walkboards spanning at least three ceiling joists on every route you will use. Acceptance: temperature under the shop reschedule threshold of 110 F, wired routes avoided, a board under every knee and foot position, and the ladder set at four to one and tied off per 29 CFR 1910.23; at or above 100 F the shop default is 20 minutes in and 10 out with water. Wrong looks like a tech kneeling between joists and putting a leg through a bedroom ceiling; stop rule, at or above 110 F come out and rebook to the first two hours of daylight, and where splices are open that zone is not worked. Hazard: with no general industry heat standard the duty runs through the General Duty Clause at 29 USC 654(a)(1), and contacting a conductor is qualified-person work under 29 CFR 1910.333(b)(2), so if nobody on site is qualified the attic waits for an electrician.

Step 3 - Identify the insulation before you disturb any of it. Look at the loose fill under a headlamp: fiberglass is fibrous and springy, cellulose is gray shredded paper, and a granular material in pebble or accordion-shaped flakes, gray to gold to brown, is presumed vermiculite. Acceptance: type named on the ticket and photographed, with fill depth measured and recorded at three marked points inside each zone you intend to strip. Wrong looks like a tech deciding a granular fill is probably perlite and running a vacuum hose through it; stop rule, any granular fill or a fill you cannot name means nothing is touched and the customer is told in writing the same day, because vermiculite attic insulation is presumed asbestos-containing until a licensed inspector says otherwise. Hazard: this route is inhalation only, so gloves and eye protection do nothing for it and non-disturbance is the control.

Step 4 - Wet the whole contaminated area and let it dwell before anything moves. Working from the hatch outward so you never back over untreated material, mist droppings, staining, nest material and the fill surface with an EPA-registered disinfectant at its label dilution, or with the bleach dilution in CDC's current rodent cleanup guidance, which is the page to pull. Acceptance: every square foot of every zone visibly wetted with no dry patches, and a timed dwell of at least the 5 minutes CDC states or the product's own label contact time, whichever is longer. Wrong looks like a spray-and-bag pass where the wetting was a gesture and the material still lifts; stop rule, material that dries before you reach it gets re-wetted and its clock restarted. Hazard: this is the first step where an aerosol is possible, so a half-mask respirator with N100 or P100 filters goes on before the sprayer does, under a written program with medical evaluation and fit testing per 29 CFR 1910.134, and if nobody on the crew is in that program the crew does not do the work rather than doing it bare; never mix bleach with an ammoniated cleaner, which liberates chloramine gas, and if that happens everyone leaves through the hatch and the attic ventilates before anyone returns.

Step 5 - Remove wet, bag wet, and keep the shop vacuum and the broom off the ladder. Pick up droppings and nest material with a gloved hand or a wetted towel, roll contaminated batts inward on themselves, cut saturated fill out in wetted sections, and bag at the point of removal, double bagged and closed before the bag leaves the zone. Acceptance: bags sealed and counted, no dry material handled at any point, and any vacuuming done only after wetting and only with a HEPA-filtered vacuum. Wrong looks like a shop vacuum exhausting fine material through a filter never rated to hold it; stop rule, no HEPA vacuum on the truck means residual fines stay and get wiped at step 6. Hazard: the contact and ingestion routes are live here alongside the aerosol, so nitrile gloves stay on, nothing is eaten or drunk in the attic, and gloves come off and hands wash before anyone touches a phone or a truck door.

Step 6 - Disinfect the surfaces, then close out what the dead host left behind. Wipe framing, duct exteriors, top plates and stored items with the same disinfectant, then check for rodent mites and fleas, which leave a carcass or an abandoned nest and move down through the same ceiling penetrations the rodents used. Acceptance: every reachable hard surface in each zone wiped at the label contact time, and either no ectoparasite evidence on a white card check at each ceiling penetration or a labelled crack and crevice or void treatment where the label names that site and that pest. Wrong looks like an attic cleaned to a photograph while the customer starts getting bitten a week later; stop rule, a product that does not name the site or the pest is not applied, because applying anyway is use inconsistent with the labeling. Hazard: applying a residual overhead puts product back in your own face, so eye protection and the label's own respiratory requirement both apply here, which is a separate selection from step 4's biological aerosol.

Step 7 - Put the insulation and the building back, and prove it works. Reinstall fill in every zone you stripped, reseat any batt you moved, replace covers on any box or fan you opened, re-close any circuit opened at step 2, and latch the hatch with its weatherstrip and insulation dam back in place. Acceptance: restored depth at or above the recorded depth at each of the three marked points in each stripped zone, measured with a ruler rather than eyeballed, every cover back on, bath and range fans running when switched, attic light working, hatch latching. Wrong looks like fill blown deep at the middle of a zone and shallow at the eaves, where nobody measures; stop rule, any mark below its recorded depth gets fill added and re-measured before you come down. Hazard: energizing a circuit is where a fault you did not find announces itself, so the qualified person who opened it closes it, stands to the hinge side of the panel rather than square in front, then confirms the attic light and the bath fan both run, because the point of restoring that circuit is the fan.

The record this produces

On the ticket and the attic sketch: species and the evidence for it, zones numbered with square footage each, insulation type with photo, depth at three marked points per stripped zone before and after, attic temperature at the hatch and far end with the time of day, respirator model and filter class with the wearer's fit-test date, disinfectant product with EPA registration number, dilution and the contact time actually observed, bag count, any ectoparasite treatment with product, site and rate, restoration verifications, and every stop rule that fired with its measured value.

The service manager reads the before and after depth columns, because a cleanup that never restores depth is the most common source of a spring callback that has nothing to do with rodents.

Worked pass: 1,150 square foot attic, house mouse, three zones

Single-story house, hatch in the hallway ceiling, exclusion completed nine days earlier with twelve entry points sealed off. Droppings are rice-grain sized with pointed ends and the gnawing is fine, so the species is recorded as house mouse rather than deer mouse. That keeps the job out of the elevated hantavirus category; the shop runs N100 on every attic cleanup regardless. Contamination sketches into three zones: zone A at the hatch, 60 square feet; zone B along the north soffit run, 180 square feet; zone C at the bath fan chase, 40 square feet. That is 280 square feet, 24 percent of the 1,150 square foot attic floor.

Step 2 fails. At 1:40 pm the attic reads 116 F at the hatch and 121 F at the north end, against the 110 F reschedule threshold. The stop rule fires, nobody goes past the hatch, and the job rebooks to 6:40 the next morning, when it reads 82 F and 84 F, both under 100 F, so no work-rest cycling is needed.

Step 3 finds gray shredded cellulose, photographed and named. Zone B is the only zone where the fill is urine-saturated and has to come out; its three marks read 9 in, 9 in and 10 in. Zones A and C are surface contamination over intact fill and are wiped rather than stripped.

Step 4 runs a quaternary disinfectant whose label states a 10 minute contact time. CDC states a 5 minute soak, so the longer of the two governs and the timer is set at 10 rather than 5. Actual dwell is 12 minutes on zone A, 11 on zone B and 12 on zone C, all three clear of the governing 10. Step 5 produces 11 sealed double bags, 8 from the stripped zone B fill and 3 from zones A and C. Step 6 finds no mite or flea evidence on the white card check at the two ceiling penetrations in zone C, so nothing is applied and the ticket records the check.

Step 7 restores zone B to 10 in, 9.5 in and 10 in at the same three marks. Each clears its own recorded depth - 10 against 9, 9.5 against 9, 10 against 10 - so the gate passes at all three points rather than on an average. The bath fan runs, the attic light works, no circuit was opened at step 2 so none needed closing, and the hatch latches with its dam reseated.

References

• CDC rodent cleanup guidance, for the wet-then-soak method, the soak time and the current bleach dilution
• 29 CFR 1910.134, respiratory protection under a written program; 29 CFR 1910.23, portable ladders; 29 CFR 1910.333(b)(2), qualified-person electrical work practices
• EPA guidance on vermiculite attic insulation, which directs that it be presumed asbestos-containing and left undisturbed
• See related: Rodent Exclusion and Trapping; Rodent Bait Station Placement and Servicing; Crawlspace Inspection and Treatment Standard