The Rodent-Contaminated Work Area SOP

Purpose

This procedure gets a technician from "there are mouse droppings where I have to work" to a clean work area without anyone breathing rodent dust, and it decides, at a fixed point, when the contamination is too heavy for a tech to handle. Without it, techs clean the way they clean everything else, with a shop vac or a brush, which is the exact act that aerosolizes hantavirus. Why each control exists is explained in the owner card; this SOP is the standing run. See related: Rodent Droppings and Hantavirus for the Trades.

Scope

Covers: droppings, urine, nests and dead rodents inside the tech's own work area: an equipment cabinet, a closet, a sink base, a short reach of attic or crawlspace around the unit being serviced.

Does not cover: whole-attic or whole-crawlspace cleanup, removal of contaminated insulation, or duct cleaning. Those are heavy contamination by this SOP's definition and go to a remediation or pest contractor. Crawlspace entry itself is gated by The Crawlspace Entry Hazard Check SOP, which runs first. Dead animals large enough to smell from outside the space are covered in Dead Animals in Walls, Ducts and Crawlspaces.

Roles and responsibilities

Procedure

Step 1. Assess and classify before touching anything. From the doorway or access, with a flashlight and without entering, look over the floor, the equipment, the corners and any insulation in view. Classify using these shop defaults, tunable by the owner: Light is scattered droppings over under 2 sq ft with no nest; Moderate is a nest, a dead rodent, urine staining, or droppings up to 10 sq ft; Heavy is anything over 10 sq ft, nested insulation, or contamination continuing out of sight. Acceptance: a class written in the job note before step 2. Wrong looks like a tech who cannot see the extent; unseen extent is Heavy until seen. Stop rule: Heavy, call the office and do not proceed past step 2. Hazard: opening the door is already a disturbance, so do it slowly and stay out of the space.

Step 2. Ventilate for 30 minutes with nobody inside. Open every door, window and access that serves the space. Do not aim a fan at the droppings. Leave and work elsewhere. Acceptance: 30 minutes by the clock from the last opening, with the start time in the note. Wrong looks like a closet with no opening to the outdoors; in that case open the doors in the path to the nearest exterior door and extend the wait to 45 minutes as a shop default. Stop rule: if a Heavy area was found, ventilate anyway while the office calls, because it protects the household. Hazard: opening a stuck attic hatch or window from inside the space puts the tech in it before airing; if that is the only way, wear the respirator from step 3 for that one act.

Step 3. Put on PPE and check the seal. Nitrile or rubber gloves, safety glasses, and for Moderate a half-face respirator with P100 filters under the shop's written program per OSHA's 29 CFR 1910.134, plus disposable coveralls if the tech will kneel or lie in the area. Light may use the same respirator or a voluntary N95. Acceptance: a user seal check passes (no leak felt on a negative-pressure inhale) and the fit-test date on file is within 12 months. Wrong looks like a beard under the seal or a lapsed fit test. Stop rule: no current fit test means no Moderate work; the area goes to the office as if Heavy. Hazard: coveralls and a respirator raise heat load sharply in an attic or a summer closet; work in short spells, and leave the space before removing the respirator.

Step 4. Isolate the equipment, then wet everything. If the contamination is inside equipment (a blower compartment, a condensing unit base, an opener housing), lock its disconnect off first (29 CFR 1910.147 for moving parts) and prove the control circuit dead with a meter proved on a known live source before and after, per NFPA 70E-2021, 120.5, with work practices at 29 CFR 1910.333(b)(2). Then spray droppings, stains, nests and dead rodents with fresh 1 part bleach to 10 parts water, or a disinfectant labeled for viruses, until soaked. Acceptance: no dry dropping visible, and every visible surface darkened by liquid. Wrong looks like beads sitting on a dusty nest. Stop rule: re-spray until soaked. Hazard: bleach in the eyes and on skin, so glasses stay on; never mix it with another cleaner, because ammonia-based products release chloramine gas in a closed space.

Step 5. Wait 5 minutes. Set a timer for CDC's 5-minute contact time and leave the material alone. Acceptance: 5 minutes elapsed from the last spray, logged. Wrong looks like a tech who starts wiping at two minutes because the job is running late. Stop rule: if anything was disturbed early, re-spray and restart the clock. Hazard: none new at this step; it is a wait. The respirator stays on if the tech remains in the space, and a hot space is a good reason to step outside for the five minutes.

Step 6. Remove with paper towels, and look past the edge. Pick up droppings and soaked material with paper towels into a plastic bag. Re-soak a nest and lift it whole. Lift dead rodents with a towel and bag each separately. As each layer comes up, look at what was under it and beyond it. Acceptance: the class from step 1 still holds once the material is off. Wrong looks like droppings continuing under insulation, behind a panel or down a duct. Stop rule: if the extent now exceeds the step 1 class, reclassify; if it is now Heavy, stop removing, bag what is already loose, disinfect only the part already cleared (step 7), finish steps 8 to 10, and call the office. Hazard: sheet-metal edges in cabinets cut through nitrile, so wear cut-resistant gloves over the nitrile when reaching into a cabinet; no broom, no vacuum, no compressed air.

Step 7. Disinfect the area and the tools. Spray and wipe the floor, the cabinet interior, adjacent surfaces and every tool that touched the area. Mop or sponge larger floors with fresh solution. Acceptance: every surface that held droppings has been wiped wet with solution, and tools are wiped before they go back in the bag. Wrong looks like a flashlight or a nut driver going back in the tool bag dry. Stop rule: re-wipe. Hazard: bleach residue on bare metal corrodes it, so wipe equipment parts with water after the contact time; chemical contact on skin is the risk here, and gloves stay on.

Step 8. Bag and seal. Put the waste bag inside a second bag, seal both, and put them in the customer's outdoor garbage with their permission, or in the shop's dumpster, following local rules. Acceptance: double-bagged and sealed, out of the living space. Wrong looks like a single torn bag. Stop rule: re-bag. Hazard: a tear lets wet material contact skin or clothing; do not compress the bag against your body to squeeze the air out.

Step 9. Doff and wash. Wash gloved hands in solution or soap and water. Remove coveralls by rolling them inside out away from the body and bag them. Remove outer gloves, then glasses, then the respirator by its straps, then inner gloves, and bag the disposables. Wash hands and forearms with soap and warm water. Acceptance: hands washed after the last glove comes off, and nothing worn in the area rides in the cab. Wrong looks like a respirator pulled off by its facepiece with gloved hands. Stop rule: if the order broke, wash face and hands again. Hazard: doffing is where contamination reaches the face; keep it slow and do it outside the space.

Step 10. Return the area and the equipment. Restore what was removed, close the cabinet, and only then remove the lock and restore power. Stand to the side of the cabinet, not square in front of it, as power comes back. Verify the protective function you disturbed: with the blower door removed, the door safety switch must keep the blower from running. Acceptance: the equipment runs a full cycle with panels on, and the door switch test passes. Wrong looks like a blower that runs with the door off. Stop rule: if the area was reclassified Heavy, the equipment does not return to service, because running a blower through a contaminated duct spreads the dust through the house; tag it and tell the customer why.

The record this produces

The job note carries: the class at step 1 and any reclassification at step 6, with what changed it; the 30-minute ventilation start time; respirator type and fit-test date; the contact time observed; disposal location; whether equipment was locked out and restored; and any escalation with the contractor named. The office reads it to book follow-up. The owner reads it for program gaps. The date matters most months later: if the tech gets fever and muscle aches within eight weeks, this note is what tells the clinician and the shop exactly when and where the exposure happened.

Worked pass: a furnace in a basement utility room, October

Step 1. HVAC tech, no-heat call, gas furnace in an unfinished basement in rural Colorado. With the blower door off at arm's length, the tech sees a nest in the blower compartment, about a dozen droppings on the compartment floor and urine staining on the blower housing. No other evidence in view. Class: Moderate, written at 9:12.

Step 2. Basement door and two hopper windows opened at 9:14. Tech stages parts in the truck. Released at 9:44, 30 minutes.

Step 3. P100 half-face, fit test dated in May, seal check passes. Gloves, glasses, coveralls.

Step 4. Furnace service switch off, locked and tagged; meter proved on a known live receptacle, read zero at the transformer primary, proved again on the receptacle. Nest and droppings soaked at 9:52.

Step 5. Timer to 9:57.

Step 6. Fails. The nest comes out whole and the compartment floor is wiped. With the filter rack opened, the tech's light shows droppings continuing into the return duct, beyond arm's reach and out of sight around the first elbow. That exceeds Moderate: contamination continuing out of sight is Heavy. Removal stops; the loose material already lifted is bagged. Tech calls the office at 10:06.

Steps 7 to 9. Compartment, rack and tools disinfected. Waste double-bagged into the outdoor bin. Doffed outside the basement door, hands washed at 10:21.

Step 10. Fails by design. The furnace stays off, locked out and tagged "do not operate: rodent contamination in return duct." The customer asks the tech to just run it. The tech explains that the blower would pull the duct's contents through every register in the house, records the refusal of that request in the note, and the office books a duct cleaning contractor for two days out. The blower motor that caused the no-heat call is replaced on the return visit, after written clearance.

References

• CDC, How to Clean Up Rodent Urine and Droppings (30-minute ventilation, bleach ratio, 5-minute soak, no sweeping or vacuuming)
• OSHA, 29 CFR 1910.134 Respiratory Protection; 29 CFR 1910.147 Control of Hazardous Energy; 29 CFR 1910.333 Selection and Use of Work Practices
• NFPA 70E-2021, 120.5 (verifying absence of voltage)
• See related: Rodent Droppings and Hantavirus for the Trades
• See related: The Crawlspace Entry Hazard Check SOP