Sodium Hypochlorite Mix and PPE Standard

Purpose

A mix that lands off target does one of two things: too weak and the algae is back on the siding in six weeks with the customer calling to ask why they paid for a wash that didn't work, or too strong and it strips wax off a car in the driveway, yellows a shrub bed, or eats granules off a roof the shop just warrantied. PPE tossed in the truck instead of worn turns a routine mixing pour into an eye or skin exposure on the one day the tech is in a hurry.

This procedure keeps the same mix coming out of the tank regardless of which tech runs it, and keeps PPE a standing habit instead of a call made after concentrate is already open. Sodium hypochlorite (SH) is a real chemical hazard on its own, skin and eye burns on contact, fume exposure from the chlorine odor a fresh pour releases, fabric and metal damage from drift, with a second hazard layered on top if it ever meets an incompatible product, which the chlorine gas risk SOP owns. This procedure is the daily discipline that keeps that second hazard from getting a chance to start.

Scope

Covers mixing SH concentrate into a working dilution for siding, roof, or hard-surface work, the PPE standard for anyone handling concentrate or fresh solution, and labeling, loading, and end-of-job decontamination.

Does not cover the dilution math, owned by the sodium hypochlorite dilution and strength reference, the incompatible-mixing gas hazard, owned by the chlorine gas risk SOP, or first aid after an exposure, owned by the chemical splash and exposure response SOP. This procedure hands off to each the moment its own scope ends.

Roles and responsibilities

Procedure

1. Mix outdoors or in open air, and stage full PPE before the cap comes off any concentrate container. Never mix inside a garage, van interior, or any space without free airflow; a fresh SH pour releases a chlorine odor that builds fast in a closed space. Position so a light breeze carries fumes away from your face rather than into it, don chemical splash goggles or a face shield, chemical-resistant gloves (not vinyl, which SH degrades with repeated use), a chemical-resistant apron, and closed-toe boots, and stage a gallon of clean water or an eyewash bottle within arm's reach. Acceptance: mixing location is open air with airflow carrying away from the mixer, PPE fully donned and water reachable without a step taken, confirmed before the cap is touched. What wrong looks like: goggles pushed onto the forehead "for now," gloves grabbed after the pour starts, or mixing inside a closed van "just to get out of the rain." Stop rule: no open-air location, no PPE, and no staged water, no cap comes off, not "just this once." Hazard: the first two seconds after uncapping is when a heavy pour or a stuck cap gives a face-height splash and a sharp burst of fumes, and PPE and airflow only work already in place, and if that does not hold, then - the staged water is what limits a splash exposure to seconds instead of minutes and moving upwind is what limits a fume exposure the same way; see the chemical splash and exposure response SOP.

2. Confirm source strength and target percentage in writing before any math. Read the product's own label or SDS for its actual available-chlorine percentage (commonly on the order of 12.5 percent professional strength, though this varies by manufacturer and lot and must be read off the container in hand), match it to the job's target from the dilution reference, and write both on the batch ticket. Acceptance: source and target percent both written before pouring, for example "12.5 percent source, 2 percent target, siding." What wrong looks like: mixing "by feel" from a ratio remembered off a different job, or a roof run at siding strength. Stop rule: no written source and target, no mixing. Hazard: low, this is a documentation gate, and step 1's PPE stays on through it since concentrate is already open on the tailgate.

3. Mix concentrate into water, in a container dedicated to this chemical alone. Fill with the calculated water volume first, then add concentrate slowly down the container wall, never the reverse, and never into hardware that has carried an acid-family product (a rust remover, an oxalic brightener) without the compatibility check in the SDS review and product substitution SOP first. Acceptance: water in before concentrate, container's label history shows this chemical only. What wrong looks like: concentrate poured first, splashing harder off a dry bottom than a slow pour down a wet wall. Stop rule: any container without a clean single-chemical history is quarantined and run through that compatibility check, never used on the assumption it was "probably fine." Hazard: splash-back scales with pour height and speed, pour low and slow and stand upwind, and if that does not hold, then - a face shield rather than goggles alone is the next layer, since a shield also stops a stream, not just a mist.

4. Meter the pour to the ticket target and confirm before loading the rig. Measure concentrate with a marked container or metering pump to within about 10 percent of the calculated figure, and where a chlorine test strip is available, confirm the mixed solution reads in the expected band for that target. Acceptance: pour within tolerance, strip in the expected band when used. What wrong looks like: eyeballing "close enough" on a batch headed for a roof, where overstrength cooks shingle granules and understrength means a callback. Stop rule: a pour that misses tolerance is not corrected by adding "a little more," which cannot be measured back out; start over from a fresh, measured pour. Hazard: identical splash exposure to step 3, PPE stays on through metering.

5. Load and route lines so the SH system never shares hardware with an acid-family product on the same rig. Secure the mixed container, connect a hose and injector dedicated to SH only, and where an acid-based product is also carried that day, route it through its own pump-up sprayer on the opposite side of the rig, never the same line with a rinse in between. Acceptance: SH and any acid-family product on separate hoses, injectors, and secured compartments. What wrong looks like: one pump-up sprayer doing double duty across both chemical families because the rig only carries one. Stop rule: a single-sprayer rig with two chemical families runs one family per visit, or the sprayer goes through the full purge-and-rinse sequence in the chlorine gas risk SOP between uses, verified before it carries the second chemical. Hazard: this is the setup step for gas generation, and a hose or sprayer that carried SH and now carries acid without a verified purge is a live gas source before the first spray, and if that does not hold, then - the chlorine gas risk SOP's response sequence is what a tech runs the moment a sharp, pool-like odor shows up where it should not.

6. Crew lead confirms the batch ticket and every handler's PPE before the first trigger pull. The crew lead, not the mixer, reads source and target against the job type, and visually checks every chemical handler is in full PPE. Acceptance: crew lead's initials on the ticket and PPE visually confirmed on each handler, both before the first spray. What wrong looks like: the mixer's own initials standing in for the second signature, which cannot catch an error the mixer already believes is correct. Stop rule: no second signature in person, no first spray; a remote "go ahead" by phone does not satisfy this step. Hazard: none unique, this step verifies steps 1 through 5 actually held.

7. Decontaminate the mixing area and log unused concentrate at job close. Rinse the mixing container and any splash surface with water, recap and secure remaining concentrate in its original transport container, and log the volume remaining on the ticket. Acceptance: surface visibly clear of residue, concentrate resealed, remaining-volume figure logged. What wrong looks like: leftover diluted mix sitting in an unlabeled tank overnight, which the next crew treats as plain water. Stop rule: leftover mix is labeled and dated for reuse within the shelf-life window in the storage and shelf-life reference, or disposed of per that reference; never left ambiguous. Hazard: residue on the mixing surface stays reactive to whatever touches it next, gloves stay on through cleanup, not just the pour.

The record this produces

One batch ticket per mixed load, read by the crew lead that day and the office afterward.

Fields: source percentage and product name, target percentage and job type, measured concentrate volume, mixer's initials, strip reading where taken, crew lead's sign-off, remaining concentrate volume at close.

The crew lead reads source and target before the first spray, since that is the only check standing between a mixing slip and a strip of dead grass or a stripped roof. The office reads the remaining-volume trend across jobs; a shop consistently logging more concentrate used than the dilution math predicts is either running mixes hot or losing product to a leak, and either is worth catching before a customer does.

Worked pass: two-story vinyl-sided home, moderate algae streaking

Step 1. Tech dons goggles, gloves, apron, boots, and stages a water jug on the tailgate before touching the concentrate cap. PASS.

Step 2. Label reads 12.5 percent sodium hypochlorite. Job is moderate siding algae, so the dilution reference's siding target of 2 percent applies. Ticket written: "12.5 percent source, 2 percent target, siding." PASS.

Step 3. Five-gallon tank filled with water first, then 0.8 gallon of concentrate poured slowly down the wall for the calculated 2 percent ratio. Tank has carried SH only. PASS.

Step 4. Test strip reads in the expected band for a 2 percent mix. Pour within tolerance. PASS.

Step 5. This job also carries an oxalic-acid rust remover for sprinkler stains on the driveway. Two dedicated pump-up sprayers, one per chemical family, SH runs to its own injector. No shared hardware. PASS.

Step 6 FAILED and took its stop rule. The crew lead was finishing a job across town and texted "looks fine, go ahead" instead of checking in person. The tech saw the ticket had no in-person sign-off and called it in rather than pulling the trigger. The crew lead drove over, checked both techs' PPE, caught that the second tech had pushed his goggles up to read a text ten minutes earlier, had him reseat them, and signed the ticket eleven minutes after the original "go ahead." First spray happened after the signature.

Step 7. At job close, 0.6 gallon of concentrate remained, resealed and logged. Mixing tank rinsed and left visibly clean.

What step 6 bought: a remote "go ahead" would have let the second tech spray for eleven minutes with his goggles up, exactly the window a splash exposure needs. The delay cost eleven minutes of labor and prevented an eye exposure PPE alone, worn wrong, would not have stopped.

References

• Product SDS and label, Sections 7 and 8 (handling and storage, exposure controls), for the specific concentrate in hand; strength and classification vary by manufacturer and lot
• OSHA 29 CFR 1910.132 and 1910.133, general PPE and eye/face protection requirements
• ANSI Z358.1 for emergency eyewash and shower equipment placement and response time
• See related: sodium hypochlorite dilution and strength reference, chlorine gas risk from incompatible chemical mixing, chemical splash and exposure response