Chemical Compatibility Chart: What Can Be Stored Together

What Is a Chemical Compatibility Chart?

A chemical compatibility chart is a reference tool that shows which chemical classes can be safely stored together and which combinations create dangerous reactions — fires, explosions, toxic gas release, or violent heat generation. These charts organize chemicals by hazard class and use color-coded or symbol-based grids to indicate compatible, incompatible, and conditionally compatible pairings at a glance.

A maintenance supervisor at a pool supply company once told me about the day a new hire stacked calcium hypochlorite next to brake fluid on the same shelf. Nobody noticed until the shelf started smoking. They got lucky — it was caught in time. But every year, preventable chemical reactions injure workers and damage facilities simply because someone stored the wrong chemicals next to each other. A compatibility chart posted in your storage area transforms a guessing game into a 5-second safety check. It's one of the simplest and most effective tools in workplace chemical safety.

Chemical Compatibility Matrix

This matrix covers the major chemical hazard classes. Green means compatible for storage. Red means never store together. Yellow means conditional — check individual SDSs for specific combinations.

Chemical Class	Flammable Liquids	Acids (inorganic)	Bases/Caustics	Oxidizers	Organic Peroxides	Toxics
Flammable Liquids	OK	NO	Check SDS	NO	NO	Check SDS
Acids (inorganic)	NO	OK*	NO	NO	NO	Check SDS
Bases/Caustics	Check SDS	NO	OK	NO	NO	Check SDS
Oxidizers	NO	NO	NO	OK*	NO	Check SDS
Organic Peroxides	NO	NO	NO	NO	OK*	NO
Toxics	Check SDS	Check SDS	Check SDS	Check SDS	NO	OK*

*Within the same class, some chemicals are still incompatible. Nitric acid (oxidizing acid) must be separated from acetic acid (organic acid). Chromic acid and sulfuric acid react violently. Always verify specific chemical pairs using SDS Section 10 (Stability and Reactivity).

Dangerous Chemical Combinations in Common Workplaces

These aren't exotic lab scenarios. These combinations happen in auto shops, cleaning supply closets, and maintenance rooms every week:

Chemical A	Chemical B	Reaction	Found In
Bleach (sodium hypochlorite)	Ammonia-based cleaners	Chloramine gas — toxic, causes respiratory damage	Janitor closets, bathrooms
Bleach	Acids (muriatic, vinegar, rust removers)	Chlorine gas — potentially fatal	Cleaning supply rooms, pool maintenance
Hydrogen peroxide (concentrated)	Acetone or organic solvents	Explosive peroxide compounds	Labs, beauty supply, manufacturing
Pool chlorine (calcium hypochlorite)	Brake fluid (polyethylene glycol)	Spontaneous fire	Maintenance storage areas
Potassium permanganate	Glycerin or antifreeze	Spontaneous ignition	Water treatment, automotive shops
Nitric acid	Organic materials (wood, paper, rags)	Fire risk — nitric acid is a strong oxidizer	Metal finishing, etching operations

The bleach-ammonia combination alone sends thousands of people to emergency rooms annually. Many workers don't realize that common cleaning products contain these chemicals — which is exactly why reading Safety Data Sheets before storing products together is critical, not optional.

How to Use a Compatibility Chart in Your Workplace

So you've got the chart. Now what? Printing it and filing it in a drawer accomplishes exactly nothing. Here's how to make it actually useful:

1. Post the chart visibly — laminate it and mount it at eye level in every chemical storage area, supply closet, and receiving dock
2. Train employees on the chart — during chemical safety training, walk through the chart and explain what each color/symbol means with real product examples from your inventory
3. Cross-reference before storing — when a new chemical arrives, check its hazard class against every chemical already in the proposed storage location before placing it
4. Check SDS Section 10 — the compatibility chart covers broad classes; Section 10 (Stability and Reactivity) of each product's SDS lists specific incompatible materials for that chemical
5. Audit quarterly — chemicals get moved, new products arrive, and storage areas drift from their original organization; a quarterly walkthrough catches problems before they react

Digital SDS tools make the cross-referencing step dramatically faster. With MySDS Manager, you can search for any product and immediately see its SDS Section 10 incompatibilities — no flipping through binders or hunting for the right page. When receiving a new chemical, a 30-second search tells you exactly where it can and cannot be stored.

Storage Segregation Methods

Once you've identified incompatible chemicals, you need physical separation. Several methods work:

• Separate cabinets — the most common approach; flammable cabinets for flammables, acid cabinets for corrosives, each physically isolated
• Distance separation — NFPA recommends at least 20 feet between incompatible chemical groups when cabinets aren't used
• Barrier walls — non-combustible walls between storage areas for large quantities
• Secondary containment — trays and dikes that prevent leaked chemicals from flowing into contact with incompatible substances
• Separate rooms — dedicated chemical storage rooms for each major hazard class in facilities with significant chemical inventories

Vertical separation matters too — and this is one people forget constantly. Never store acids on shelves above other chemicals. Picture a leaking acid container dripping onto an incompatible chemical below. That's not a hypothetical; it's exactly the scenario that caused a warehouse evacuation in Ohio a few years back. Corrosives go on the lowest shelves. Always.

Building Your Facility-Specific Chart

Generic charts cover broad chemical classes, but your workplace benefits from a customized version that references actual products by name:

1. List every chemical product by name and manufacturer
2. Identify each product's hazard class from its SDS Section 2
3. Check Section 10 for specific incompatibilities beyond the general class
4. Map your storage areas to verify no incompatible products share a cabinet, shelf, or containment area
5. Create a simplified reference — a poster that says "These products go in Cabinet A, these in Cabinet B, these in the acid cabinet" is more actionable than a generic matrix

Frequently Asked Questions

Can acids be stored with other acids?

Not always. While most inorganic acids (hydrochloric, sulfuric, phosphoric) can be stored together, oxidizing acids (nitric acid, perchloric acid, chromic acid) must be separated from non-oxidizing acids and from organic acids (acetic acid, formic acid). Oxidizing acids stored near organic materials — including organic acids — create fire and explosion risks. Always check SDS Section 10 for specific acid-to-acid compatibility.

Where should I post a chemical compatibility chart?

Post the chart anywhere chemicals are stored, received, or transferred: main chemical storage rooms, supply closets, receiving docks, maintenance shops, and janitor closets. The chart should be visible without needing to open cabinets or move objects. Laminate it to protect against chemical splashes. Include it in your written HazCom program as a reference document.

How do I find compatibility information for a specific chemical?

The Safety Data Sheet is your primary source. Section 10 (Stability and Reactivity) lists "incompatible materials" and "conditions to avoid" for each chemical. Section 7 (Handling and Storage) provides additional storage guidance. If you use a digital SDS system, searching for a product and navigating directly to Section 10 takes seconds. For unusual chemical combinations not covered by your chart or SDS, contact the manufacturer's technical support or consult a chemical safety professional.