Methodology

1. Define the decision

We begin by identifying what the reader is trying to decide: whether two products should be combined, whether a cleaner may damage a material, how to calculate a dilution, or how a chemical should be handled. We identify variables that may change the answer, including exact formulation, concentration, quantity, temperature, ventilation, contact time, exposure route, and local rules.

2. Identify the substance or product

Common names can describe different formulations. Whenever possible, we distinguish the active ingredient from the branded product and look for a current label or SDS. A database entry for a pure compound is not assumed to describe every commercial mixture that contains it.

3. Gather evidence

We search the source hierarchy described in our Editorial Policy. Important claims are linked to public sources whenever practical. We prefer current primary guidance and check whether it applies to household, workplace, laboratory, or environmental settings.

4. Classify compatibility conservatively

Compatibility results are framed using practical categories:

• Do not mix: credible evidence indicates a dangerous reaction, harmful gas, fire, pressure, or other serious hazard.
• Use separately: sequential use may be acceptable only when label directions are followed and the first material is removed or the surface is rinsed as appropriate.
• Condition-dependent: the answer changes with formulation, concentration, surface, temperature, or another material factor.
• Insufficient evidence: we cannot support a reliable conclusion from the available information.

“No known reaction” is not treated as proof of safety.

5. Verify calculations

For calculators, we state the governing equation, define every input and output, normalize compatible units, test known examples, and check zero, negative, impossible, or out-of-range values. Outputs are rounded for usability without implying more precision than the inputs support.

6. Add limitations and escalation guidance

Each safety-sensitive page should direct readers back to the product label and SDS. Where an exposure may have occurred, the page should prioritize fresh air or immediate expert help only when supported by an appropriate authority and should not attempt to diagnose or treat an individual case.

7. Review and maintain

Pages include a modified date. We review a page after a credible correction, an authoritative source update, a product-formulation change we become aware of, or a material change to a calculator. Readers can report concerns through Contact Us.

Limits of this methodology

We do not independently laboratory-test products. Source quality and applicability can vary, and not every formulation or jurisdiction can be covered. See the Safety Disclaimer before relying on any safety-related page.

Methodology version 1.0 · Last reviewed September 6, 2026.