In brief
The real question in chemical storage is not "how much" but "next to what"; substances that react with each other must not share the same shelf or the same spill tray. The incompatibility decision is drawn from sections 7 and 10 of the safety data sheet and turned into a shelving arrangement and a store plan. This article includes a group table, shelving rules, spill trays and an inspection checklist.
Why are chemical storage rules a matter of "neighbours"?
In a dyehouse store, a container of bleach falls from a shelf and mixes with an acidic descaler on the shelf below, and chlorine gas spreads within a short time. In a maintenance workshop, hydrogen peroxide and solvent sit in the same cabinet. In both cases the chemicals themselves are ordinary products on their own; what creates the danger is putting them side by side. Chemical storage rules are therefore first and foremost an arrangement of neighbours.
Art. 7 of the Regulation on Health and Safety Measures in Work with Chemical Substances requires the employer to make the necessary arrangements for storing hazardous chemicals and their waste and residues, and to prevent contact between chemical substances that may affect each other. The same article also lists preventing the presence of hazardous quantities of chemically unstable substances and the presence of ignition sources. The Regulation does not list one by one which substance must be separated from which; it leaves this decision to the products' safety data sheets and the risk assessment.
How is a chemical incompatibility chart used?
An incompatibility chart is a decision tool that divides chemicals into hazard groups and shows which group must be kept away from which. The order of use is as follows:
- Take an inventory. List every product in the store with its quantity and location. For the inventory columns, see our article on preparing a chemical inventory.
- Read the safety data sheet. The pictograms and H statements in Section 2 give the group, Section 7 gives the storage conditions, and Section 10 gives the conditions to avoid and incompatible materials. We explained how to read these sections in our article on how to read a safety data sheet.
- Assign each product to a group. A product with more than one hazard is placed according to its most restrictive group.
- Check against the chart. Compare the groups of products on the same shelf or in the same tray using the chart.
- Draw the store plan. Prepare a simple sketch marking shelves, cabinets and trays by group and post it at the store entrance.
The table below is a general starting point; the final decision is always made according to Section 10 of the product's own data sheet.
| Group (clue on the data sheet) | Keep separate from | If they come together |
|---|---|---|
| Acids (corrosive pictogram, H314, H290) | Bases, hypochlorite, cyanide and sulphide salts, reactive metals | Heat and splashing; chlorine, hydrogen cyanide or hydrogen sulphide gas |
| Oxidising acids (nitric, perchloric acid) | Organic acids, flammable liquids, paper and wood | Fire, violent reaction |
| Bases (sodium hydroxide, ammonia solution) | Acids; aluminium and zinc containers; hypochlorite | Heat; hydrogen gas; chloramines |
| Oxidisers (flame over circle pictogram: peroxides, nitrates, permanganate, hypochlorite) | Flammable liquids, organic materials, reducing agents, metal powders | Fire, explosion |
| Flammable liquids (flame pictogram: solvents, thinners, alcohols) | Oxidisers, heat and ignition sources | Fire |
| Water-reactive substances (H260, H261, EUH014) | Water, aqueous solutions, damp environments, acids | Flammable gas, heat |
| Compressed gas cylinders (gas cylinder pictogram) | Oxygen cylinders and flammable gas cylinders from each other; heat sources | Fire, explosion |
The level of separation in the table is chosen according to the quantity in the store and the risk assessment: separate secondary containers in the same cabinet, a separate shelf and separate tray, or a separate room or compartment. For small quantities a separate tray may be enough, whereas quantities at drum and IBC level require physical separation.
Storing acids and bases separately: the most common mistake
Because acids and bases both carry the "corrosive" pictogram, they are put on the same shelf. Yet when the two come into contact, heat is released and splashing occurs. In practice, the rule of storing acids and bases separately means:
- Acids and bases sit on separate shelves and in separate spill trays; if they share the same cabinet, each is in its own secondary container.
- Oxidising acids such as nitric acid are also separated from organic acids such as acetic and formic acid. They are not put in the same tray just because "they're all acids".
- A corrosion-resistant, ventilated cabinet is used for acids; metal shelves corrode over time and lose their load capacity.
- Sodium hydroxide solution is not kept in aluminium containers or on aluminium shelving.
Oxidiser storage and flammable liquids
Two points are considered in the oxidiser storage decision. First, oxidisers are kept away from flammable liquids and organic materials; this includes cardboard packaging, wooden pallets and absorbent cloths. Second, many oxidisers are sensitive to heat and sunlight; the temperature limit in Section 7 is observed.
For flammable liquids, the basic rule is to keep only a day's requirement in the production area and keep the rest in a fire-resistant safety cabinet (TS EN 14470-1) or a separate flammables store. The quantities of flammable liquids that may be stored and the storage methods are set out in Art. 115 of the Regulation on the Fire Protection of Buildings. In stores where solvent vapour accumulates, an explosive atmosphere assessment may also be needed; for this, see our article on the explosive atmosphere (ATEX) document.
Chemical store layout: shelving and cabinet rules
A good chemical store layout protects products against falling, mixing and being forgotten:
- Heavy and liquid products on the bottom shelf. Corrosive liquids are not kept above eye level; large containers go on the lowest shelf.
- Shelf edges with a lip. On shelves without an edge lip, containers fall with vibration or impact. The shelf load capacity is labelled; for details, see our article on industrial racking safety.
- No alphabetical arrangement. Sorting products by name can put incompatible substances side by side. Arrangement is by group, and alphabetical within each group.
- Every container labelled. Containers decanted from large packaging also carry the product name and hazard pictogram; unlabelled containers are not accepted into the store.
- Away from heat and sun. The store is ventilated, no ignition sources are kept, and shelves in direct sunlight are not used.
- First in, first out. Products past their shelf life and those with damaged packaging are set aside; a separate, marked area is designated for empty containers.
- No eating, drinking or smoking in the store. Warning signs are posted at the entrance; for the rules on signs, see our article on health and safety signs.
Spill trays and secondary containment
A spill tray is secondary containment that limits the spread of liquid when a container is punctured or knocked over. When setting one up, pay attention to these rules:
- The tray must have a volume that can hold at least the entire contents of the largest container in it. If there are several containers, the total volume is also taken into account.
- The tray material must be resistant to the chemical it holds; polyethylene trays are usually preferred for acids.
- Liquid must not collect in the tray, and it should be checked regularly. Trays in open areas fill with rainwater and lose capacity.
- The grating over the tray must be able to bear the weight of the containers.
A tray prevents a leak from spreading; it does not clean it up. A spill kit suited to the chemicals inside should be kept next to the store. For the kit contents and response steps, see our article on responding to chemical spills.
Checklist for store inspections
A short monthly tour of the store catches deterioration of the layout early:
| Check | Yes / No |
|---|---|
| Does every product in the store have a current Turkish-language safety data sheet? | |
| Is the store plan posted at the entrance and does it match the layout on site? | |
| Are acids, bases, oxidisers and flammables on separate shelves and in separate trays? | |
| Is there any liquid build-up or cracking in the trays? | |
| Are all containers labelled and closed? | |
| Are shelf edge lips and capacity labels in place? | |
| Are flammable liquids in a safety cabinet and limited to a day's requirement? | |
| Is the spill kit complete and accessible? | |
| Is ventilation working, and are there no ignition sources? | |
| Is the eyewash or washing facility in working order? |
At paint, coating, plastics and textile finishing businesses in Bursa and the surrounding provinces, we address store layout as part of our risk assessment work; for sector-specific risks, see our chemicals and plastics sector page. For the Regulation's other obligations, read our article on the chemical substances regulation.
Frequently Asked Questions
Can acids and bases be kept in the same cabinet?
It is not recommended. Even for small quantities where it is unavoidable, each group should be kept in its own secondary container and on a separate shelf. For drums and larger quantities, use a separate cabinet or separate compartment.
Where can a chemical incompatibility chart be found?
General group charts are sufficient as a starting point, but the final decision is made according to Sections 7 and 10 of the product's own safety data sheet. Products listed as incompatible materials on the data sheet are not kept on the same shelf or in the same tray.
Why is it wrong to arrange chemicals alphabetically?
Sorting by name can put substances that react with each other side by side. First separate by hazard group, then sort alphabetically within each group.
How big should a spill tray be?
It should be able to hold at least the entire contents of the largest container in it; if there are several containers, the total volume is also taken into account. Separate trays are used for incompatible chemicals.
A risk assessment that identifies and scores hazards on site, links each measure to an owner and a date, and has a clear renewal schedule.
Bursa SİSTEMER OSGB Technical Team — written from the field experience of our OHS specialists and workplace physicians. Legal information is valid as of the publication/update date; contact us for an assessment specific to your business.