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An empty space on a shelf is not yet a suitable storage location. Acids, alkalis, oxidizing agents, or flammable liquids can be stable individually and still react dangerously when placed next to each other, leak, or are mixed together.

For safe chemical storage, therefore, not only temperature and packaging matter. Also crucial are hazard class, storage quantity, possible reactions, containment options, and protection against unauthorized access.

This guide shows how to systematically classify chemicals in the workplace, laboratory, or workshop, which substance groups should be stored separately, and what information you must check before shelving.

Why must chemicals be stored separately?

Chemicals are not separated solely because they have different names or uses. What matters is what could happen in a combined incident.

If a container becomes leaky, incompatible substances can react with each other. Possible consequences are:

• Strong heat generation,
• Fire or explosion,
• Release of toxic or corrosive gases,
• Violent foaming or splashing,
• Pressure buildup in containers,
• Damage to packaging,
• Contamination of larger inventories.

A classic example is acids and alkaline products. When larger quantities come together, the neutralization reaction can release considerable heat. It becomes even more critical when an acid reacts with a substance that produces a dangerous gas in the process.

Therefore, the storage order must not be based solely on product names, container sizes, or free shelf space. The information from the safety data sheet and the properties of the respective substance group are decisive.

Which regulations apply to chemical storage?

For the operational storage of hazardous substances in Germany, the Hazardous Substances Ordinance is particularly relevant. It requires that hazardous substances be stored or kept in such a way that neither human health nor the environment is endangered. In addition, precautions must be taken against misuse and improper use.

The TRGS 510 „Lagerung von Gefahrstoffen in ortsbeweglichen Behältern“ specifies these requirements for example:

• Bottles,
• Canisters,
• Drums,
• Bags,
• IBC containers,
• Compressed gas cylinders,
• Storage containers and safety cabinets.

It covers, among other things, general storage requirements, storage quantities, fire protection, containment facilities, and the combined storage of different hazardous substance groups.

For hazardous substances in stationary containers, additional regulations apply, including TRGS 509.

Which measures are necessary in the specific operation depends, among other things, on:

• the classification of the product,
• the stored quantity,
• the type of container,
• the storage location,
• the activity,
• possible fire and explosion hazards,
• the results of the risk assessment.

This article provides practical guidance, but does not replace a company risk assessment or expert review of the individual storage situation.

What must be checked before storage?

Before a product is placed on a shelf or in a safety cabinet, at least five sources of information should be checked.

1. Labeling on the container

Check:

• Product designation,
• GHS pictograms,
• Signal word,
• H-statements,
• P-statements,
• concentration,
• Manufacturer or supplier information.

The labeling shows which hazards generally exist. However, it is often not sufficient alone for the specific storage decision.

2. Safety data sheet

The following sections are particularly important for storage:

• Section 2: Possible hazards,
• Section 6: Measures in case of accidental release,
• Section 7: Handling and storage,
• Section 9: Physical and chemical properties,
• Section 10: Stability and reactivity,
• Section 13: Disposal.

Section 7 often specifies temperature conditions, protection from moisture or light, and requirements for containers. Section 10 shows which substances, materials, and conditions must be avoided.

3. Storage quantity

A small laboratory bottle represents a different starting situation than several canisters or a drum. With increasing quantity, additional requirements can apply to:

• Storage rooms,
• Safety cabinets,
• Fire protection,
• ventilation,
• Containment volume,
• Access restriction

arise.

The TRGS 510 therefore distinguishes, among other things, between small quantities outside a storage area and quantities for which further protective measures apply. The specific assessment must be carried out based on the hazardous substances and total quantities.

4. Container material

Not every substance is compatible with every packaging material. Chemicals can attack certain plastics, metals, seals, or closures.

Products should preferably be stored in the suitable original container. When decanting, it must first be clarified whether:

• the container and closure are chemically resistant,
• the material is suitable for the storage temperature,
• pressure can build up,
• opaque packaging is required,
• unambiguous labeling is possible.

5. Possible reaction with neighboring substances

The most important question is:

What happens if both containers become leaky at the same time?

Only this consideration shows whether substances may be stored on the same shelf, in the same cabinet, in the same storage section, or even in the same room.

Combined storage, segregated storage, and separate storage

In everyday storage, three terms are often confused.

Combined storage

In combined storage, different hazardous substances are in the same storage area without additional spatial barriers between them.

This is only justifiable if possible interactions do not cause additional hazards.

Segregated storage

In segregated storage, substances are in the same storage area or room but are separated from each other by appropriate measures.

Possible measures are:

• sufficient distance,
• separate cabinet areas,
• separate spill containment trays,
• fire-resistant partitions,
• separate storage sections.

Separate storage

Separate storage means a further spatial separation, for example in:

• a dedicated storage room,
• a separate storage building,
• a separate fire protection section,
• a separate storage container.

TRGS 510 contains a storage compatibility table for this, in which substances are assessed based on storage classes. Classification should not be based on a single pictogram, but on the full classification and product-specific information.

Can acids and alkalis be stored together?

Acids and alkalis should be stored so that they do not come into contact with each other in the event of a leak.

A reaction can generate a lot of heat. Depending on concentration, quantity, and substance, liquids can boil, splash, or damage containers.

In practice, this means for storage:

• use separate spill containment trays,
• do not store above each other,
• use suitable, chemical-resistant cabinet areas,
• check containers for material compatibility,
• clearly label strong acids and strong alkalis,
• Check safety data sheets for additional incompatibilities.

It is particularly unfavorable to place acid containers above alkali containers. If the upper container leaks, the escaping liquid can directly reach the incompatible substance group.

Not all acids are the same

The term "acid" is not sufficient for storage decisions. Some acids have additional properties, for example:

• oxidizing,
• flammable,
• highly volatile,
• toxic,
• water-reactive.

An oxidizing acid must therefore not automatically be treated like any other inorganic acid.

Not all alkaline products are the same

Even with alkalis and alkaline solids, concentration, physical state, and reactivity must be considered.

Hygroscopic solids can absorb moisture from the air, clump, or form a strongly alkaline solution. The containers must therefore remain dry and tightly sealed.

Storing oxidizing agents correctly

Oxidizing agents can cause or intensify fires, although they themselves are not necessarily flammable. They should therefore be kept away from combustible, organic, and reducing substances.

Critical proximities can arise, for example, with:

• solvents,
• oils and fats,
• paper and wood,
• organic powders,
• reducing agents,
• highly flammable substances,
• certain metals.

During storage, you should check:

• Which incompatible substances does Section 10 of the safety data sheet mention?
• Must the product be protected from heat or direct sunlight?
• Is the packaging free of organic impurities?
• Can spilled substances get into a common drip tray?
• Are there combustible materials in the immediate vicinity?

Even contaminated work tools can be problematic. A cloth, spatula, or funnel with organic residues should not be used for a strong oxidizing agent without inspection.

Storing flammable liquids and solvents

Solvents, paint components, and other flammable liquids can release vapors. These vapors can form an explosive mixture with air and ignite at ignition sources.

Especially relevant are:

• flash point,
• boiling point,
• vapor pressure,
• storage temperature,
• ventilation,
• possible ignition sources,
• electrostatic charge.

The Federal Environment Agency points out that vapors can be released into the environment during storage and handling of volatile organic compounds. The reason is, among other things, a low boiling point and high vapor pressure.

Flammable liquids should therefore not be stored next to:

• open flames,
• heat sources,
• hot surfaces,
• spark-producing devices,
• unsuitable electrical systems,
• strong oxidizing agents

stored.

Depending on the product and quantity, a suitable safety cabinet may be required. The TRGS 510 contains requirements for safety cabinets and their ventilation in the appendix.

Is a refrigerator suitable as a storage location?

An ordinary household refrigerator is not automatically suitable for flammable chemicals. Electrical components inside can be a source of ignition.

If a flammable substance requires cool storage, it must be checked whether the device used is technically suitable and operationally approved for this purpose.

Water-reactive and moisture-sensitive substances

Some chemicals react with water or humidity. This can produce:

• heat,
• flammable gases,
• corrosive vapors,
• pressure,
• hazardous decomposition products.

Such products must be stored dry and protected from contact with water.

This means, among other things:

• close containers immediately after use,
• no storage under water pipes,
• check distance to sinks and sprinkler areas,
• do not use wet equipment,
• replace damaged closures immediately,
• use suitable desiccants only according to product specification.

"Store dry" does not merely mean that the shelf is visually dry. High humidity and frequent opening can also affect product quality and safety.

For water-reactive substances, it must also be checked whether water is unsuitable as an extinguishing agent. This information can be found in Section 5 of the safety data sheet.

Toxic and health-hazardous substances

Toxic, carcinogenic, germ cell mutagenic, or reproductive toxic hazardous substances require special attention.

Possible protective measures are:

• access only for authorized persons,
• locked storage,
• clearly marked storage areas,
• documented inventories,
• as small stock quantities as possible,
• safe withdrawal procedures,
• separate storage of food and animal feed,
• quick availability of safety data sheets.

The Hazardous Substances Ordinance contains additional protection and documentation requirements for certain particularly health-hazardous substances.

Storage must also prevent misuse or improper use. An openly accessible shelf in a commonly used room is therefore unsuitable for many hazardous substances.

Containers, labeling, and spill containment trays

Good separation loses its benefit if containers are leaking, incorrectly labeled, or unsuitable.

Keep containers closed

Chemical containers should remain closed when no product is being removed. This reduces:

• evaporation,
• moisture absorption,
• contamination,
• odor nuisance,
• unintentional spillage.

Lockable containers should enable safe storage, handling, and transportation.

Never transfer into food containers

Beverage bottles, jam jars or food boxes are not suitable chemical containers.

They entail several risks:

• confusion with food,
• insufficient chemical resistance,
• unsuitable closures,
• missing labeling,
• uncontrolled reactions with the packaging material,

Labels must remain legible

It must be clearly recognizable on the container what is inside.

Handwritten abbreviations such as "acid", "cleaner" or "solution A" are not sufficient. Depending on the operational situation, the following are necessary, among other things:

• unambiguous product name,
• concentration,
• hazard labeling,
• date of filling,
• responsible party,
• if applicable, expiration date or test date.

Select suitable spill containment trays.

A spill containment tray is intended to retain leaking liquids. It must therefore:

• sufficiently large,
• chemically resistant,
• tight,
• stable,
• easily controllable,

be.

Incompatible products should not use the same spill containment tray. Otherwise, they will be mixed together at the latest during a leak.

Storing chemicals in the workroom

A workroom should not automatically be used as a chemical storage area.

According to the Hazardous Substances Ordinance, hazardous substances may only be stored there if this is compatible with the protection of employees and suitable facilities are used.

For daily needs, this means:

• Only keep necessary quantities at the workplace,
• Return supplies to appropriate storage areas,
• Do not place containers on escape routes,
• Do not permanently store chemicals in the fume hood,
• Secure cabinets and shelves against tipping over,
• Do not store heavy containers above shoulder height,
• Do not place bottles directly on the floor,
• Keep traffic and work paths clear.

A laboratory fume hood is primarily a technical workplace. If numerous bottles are permanently stored there, the airflow can be impaired and the hazard potential increased in the event of an incident.

Typical mistakes in chemical storage

Place all acids in a common compartment

Some acids have additional oxidizing or other reactive properties. The common designation "acid" is not sufficient for storage together.

Sort only by GHS pictograms

The same pictogram can cover different hazards. Additionally, H-statements, storage class, reactivity, and safety data sheet must be considered.

Arrange hazardous substances alphabetically

Alphabetical sorting is clear, but can place incompatible products directly next to each other.

Chemical compatibility takes priority over alphabetical order.

Storing incompatible substances on top of each other

A leaking container can drip onto the chemical stored below. Therefore, acids, bases, and oxidizing agents in particular should not be placed in an unfavorable vertical arrangement.

Dispose of the original packaging.

After decanting, important labels are often missing. Moreover, the new container may not be sufficiently resistant.

Do not inspect opened containers.

Closures, seals, and packaging can become damaged over time. Inspect regularly:

• corrosion,
• discoloration,
• crystal formation at the closure,
• swollen containers,
• brittle plastic surfaces,
• damaged labels,
• unusual odor.

Only procure emergency materials after a leak.

Binding agents, containment vessels, and appropriate protective equipment must be available before a product is stored or used.

Leave old and unknown chemicals undisturbed.

Unlabeled or no longer needed containers increase the risk. Unknown substances should not be opened, transferred, or mixed with other residues.

Checklist for safe storage

Check for each newly stored product:

• Is the substance clearly labeled?
• Is the safety data sheet current and accessible?
• Which storage conditions are mentioned in Section 7?
• Which incompatible materials are mentioned in Section 10?
• Which hazard pictograms and H-statements apply?
• Is the container suitable for the product?
• Must the product be protected from light, heat, or moisture?
• May it be stored together with the neighboring substances?
• Does it require a separate drip tray?
• Is the drip tray chemically resistant?
• Are ignition sources excluded?
• Is the storage area adequately ventilated?
• Is the product protected against unauthorized access?
• Are only necessary quantities kept in the work area?
• Are binding agents and emergency equipment available?
• Are containers and storage areas regularly inspected?

Safe chemical storage does not begin with the purchase of an additional cabinet. It begins with a clean inventory: What substances are present, what properties do they have, and what could happen in the event of a combined leak?

Only then can it be determined which products may be stored together, which require separate containment areas, and which must be stored completely separately.

At ChemMarkt.de you will find chemical reagents and technical raw materials with detailed product information. When storing any item, observe the labeling, the product-specific safety data sheet, and the requirements applicable to your facility.