Field results from three residential projects using Selectrocide® ultra-pure chlorine dioxide. Third-party lab analysis by EMLab P&K, AIHA and ISO accredited.
Introduction
Conventional mold remediation has a standard playbook: contain the area, tear out the affected materials, sand the framing, encapsulate, run air scrubbers, and rebuild. It works. It also takes time, costs significant money, and puts the property owner through a major disruption.
The question we wanted to answer was simpler: what happens when you treat the structure instead of demolishing it?
In 2012, Selectrocide® ultra-pure chlorine dioxide was deployed across a series of residential mold remediation projects in the San Francisco Bay Area. Air sampling, ERMI-PCR analysis, and fungal culture testing were performed before and after treatment by EMLab P&K, an independent AIHA and ISO accredited laboratory. We are presenting these results as field observations, not controlled research. Results varied between zones and projects. Where outcomes were mixed, we say so.
The Numbers Up Front
Before getting into the projects, here is what the data showed across the work:
- Strongest single result: a severely contaminated utility closet in San Jose dropped from 288,670 spores per cubic meter to 67, a reduction of more than 99.9%
- Average interior spore reduction across sampled zones in Los Gatos: approximately 47%
- ERMI score improvement in Hillsborough: 16.2 to 6.2, a 62% reduction using EPA-methodology DNA analysis
- Fungal culture reduction in Hillsborough: 10,060 to 1,700 colony-forming units, an 83% reduction
- Cost compared to conventional IICRC S520 protocol: 44 to 64% lower across five documented projects
- Demolition required: none in any of the documented projects
Project 1: Los Gatos, CA
A 3,700 square foot single-family residence was treated using one Selectrocide 2L500 packet distributed via HVAC in fan-only mode for 24 hours. Air samples were collected at 10 locations before and four days after treatment by EMLab P&K using non-viable spore trap methodology.
Six of eight interior zones showed reductions. Two zones did not improve.
The overall average interior reduction was approximately 47%. The two zones that did not improve, a lower level bath and a lower level bedroom, are worth noting. Field notes at the time indicated the single packet application across approximately 37,000 cubic feet may have been below optimal concentration for the full volume. The protocol was subsequently updated to recommend one packet per 18,500 cubic feet.
The exterior readings also increased post-treatment, which the field team attributed to seasonal outdoor variation. This is consistent with normal ambient fluctuation and is not related to the interior treatment outcome.
Project 2: San Jose, CA
This property presented a more complex situation: a single-family home with a casita and crawl space, and a utility closet that tested at 288,670 spores per cubic meter of Penicillium and Aspergillus types before treatment. That reading was more than 86 times higher than the next highest location on the property.
Four packets were used across the four zones: the main house via HVAC, the casita with fan circulation, the crawl space with open container placement, and the utility closet area with direct treatment.
Post-treatment, the utility closet reading fell to 67 spores per cubic meter.
Field notes from the application described the results in the utility closet area as tremendous, with spore counts nearly obliterated. The 24-hour sealed treatment period was complete and the solution was fully clear at the time of post-sampling, confirming the product had fully off-gassed.
Project 3: Hillsborough, CA
This property was evaluated using ERMI, the Environmental Relative Moldiness Index. ERMI is a DNA-based PCR methodology developed by EPA researchers that uses a panel of 36 fungal indicator species to produce a standardized score of overall mold burden. It is less sensitive to short-term air variation than spore trap sampling, making it a more stable measure of structural mold presence.
Dust samples were collected before treatment and three days after. The ERMI score dropped from 16.2 to 6.2.
Stachybotrys chartarum, the species commonly associated with toxic black mold, was detected before treatment and not detected after. Aureobasidium pullulans dropped from 52,000 to 2,200 spore equivalents per milligram. Cladosporium dropped from 37,000 to 4,800.
One honest note on the timing: three days is a short window for ERMI post-sampling. The methodology relies on dust accumulation, and a two to four week settling period would produce a more definitive reading. The directional improvement is meaningful but the post-treatment score of 6.2 remains near the generally accepted elevated threshold of 5.
Fungal cultures collected from surface swabs at the same property showed total colony-forming units drop from 10,060 to 1,700, an 83% reduction. Aspergillus fumigatus was eliminated entirely.
The Cost Side
Across five projects where cost data was available, the Selectrocide protocol came in at 44 to 64% below conventional IICRC S520 remediation estimates. These are contractor estimates from 2012 and have not been independently audited. They are presented as directional indicators.
The savings come from what gets removed from the scope of work. When structural framing is sound and materials are not delaminating, demolition is not required. When there is no demolition, there is no need for containment barriers, negative air machines, or post-demolition air scrubbing. CLO₂ penetrates porous surfaces, so sanding of framing and subfloors is not required. Encapsulation is not required because the oxidation process addresses spore fragments directly.
These savings are contingent on the property qualifying for a non-demolition approach. Where there is structural compromise, active water intrusion, or significant material degradation, conventional demolition may still be the right call.
What This Data Does and Does Not Tell You
These are three field projects from a single geographic region in 2012. There was no control group. Sample sizes are small. Results varied between zones and the protocol has been refined since the work was conducted.
The strongest results, the San Jose utility closet reduction and the Hillsborough ERMI improvement, are supported by accredited independent laboratory data and represent outcomes that are genuinely significant. The cost savings were consistent across all five projects.
But two zones in Los Gatos did not improve. The ERMI post-treatment score, while better, remained near the elevated threshold. One project's results were partly limited by an application concentration that was below what the updated protocol now recommends.
We present this data because we think practitioners and property owners deserve an honest picture. The product has a credible performance record in these applications. Treatment planning, concentration calibration, and zone-specific strategy all matter. Independent post-remediation testing is recommended on every project regardless of what product is used.
All laboratory analyses referenced in this post were performed by EMLab P&K, an AIHA and ISO accredited laboratory. Selectrocide products are for professional use only and must be applied in accordance with EPA registered labels and applicable safety requirements. Results will vary.
For product information or to discuss a specific project, contact us at Inquiry@selectivemicro.com or call 855-256-8299.