Which chemicals cannot be stored together?

The safe storage of chemicals is a fundamental issue in industry, in laboratories and in any company that works with hazardous substances. The improper storage of chemicals together can not only lead to costly damage, but also to serious hazards for people and the environment: Explosions, fires and the release of toxic vapours are just some of the potential consequences if chemicals are stored incorrectly. It is therefore crucial to follow the relevant regulations and safety guidelines.

Important note: The term co-storage in this article does not mean that the substances mentioned must necessarily be stored in different rooms, but rather that they must be physically separated from each other, i.e. they must not come into contact with each other.

The most important principles of chemical storage

Regardless of where in the world a manufacturing plant is located, there are regulations designed to ensure the safety of employees, protection of the environment, and public health.  As well as a legal responsibility to comply with regulations, employers have a responsibility to business stakeholders, including insurance underwriters, to minimise risks to people, property and the environment.

The regulations have a common set of principles:

• Proper Labeling & SDS: Must be available and follow GHS guidelines.
• Segregation: Incompatible chemicals (e.g., acids & bases) must be stored separately.
• Temperature & Ventilation Control: Prevent overheating or gas buildup.
• Fire & Spill Prevention Measures: Fire suppression systems and spill kits required.
• Training & Compliance Audits: Workers must be trained, and facilities inspected.

What are hazardous substances?

Hazardous substances are chemical substances that pose a risk to health or the environment due to their physical or chemical properties. They can be toxic, corrosive, flammable, explosive or hazardous to the environment. Hazardous substances are categorised into different storage classes (LGK) based on the specific hazards posed by the substances.

The storage classes according to TRGS 510

The Technical Rules for Hazardous Substances (TRGS 510) provide a detailed overview of the storage classes that form the basis for the safe storage of chemicals. The storage classes categorise chemicals into specific groups based on their hazardousness. These groups are not only categorised according to hazard potential, but also according to the physical properties of the chemicals, for example

• LGK 1: Explosives
• LGK 2: Gases
• LGK 3: Liquid flammable substances
• LGK 4: Solid flammable substances
• LGK 5: Oxidising substances
• LGK 6: Toxic and harmful substances
• LGK 8: Corrosive substances
• LGK 9: Environmentally hazardous substances

Important principles of safe storage

The principle of safe mixed storage is based on the fact that certain chemicals must not be stored next to each other due to their chemical reactions. Incorrect co-storage can lead to dangerous reactions. The aim is therefore to minimise the risk through suitable separation measures or special storage facilities.

Examples of chemicals that cannot be stored together

Acids and bases

Acids and bases are a classic example of substances that must not be stored together. These two substances often form strongly exothermic reactions on contact, which can lead to burns and dangerous vapours. Careless storage can accelerate the chemical reaction, which can endanger the health of employees and cause considerable damage to property.

Example: Sulphuric acid (LGK 8A) and caustic soda (LGK 8B). A mixture of these two substances can lead to extreme heat development, which represents a hazard.

Oxidising agents and flammable substances

Oxidising agents are chemicals that promote the process of oxidation and can ignite other substances or even cause them to react explosively. In combination with flammable substances, this can lead to fires or explosions.

Example: Hydrogen peroxide (LGK 5.1) and ethanol (LGK 3). While hydrogen peroxide is a strong oxidising agent, ethanol is highly flammable. This combination can lead to uncontrolled fire development.

Reducing agents and oxidising agents

Reducing agents and oxidising agents are two chemicals that exchange electrons in a reaction and can release a considerable amount of energy in the process. These reactions can take place in an uncontrolled manner if the chemicals are stored incorrectly.

Example: Zinc dust and potassium permanganate. This combination can cause an explosive reaction if the two substances come into contact with each other.

Acids and metals

Acids and metals often react with each other to form hydrogen gas, which can be flammable or explosive under certain conditions. Inadequate storage of these chemicals can therefore lead to considerable safety risks.

Example: Hydrochloric acid and zinc or aluminium. This reaction produces hydrogen gas, which can ignite and cause an explosion if it comes into contact with air.

Ammonium nitrate and flammable substances

Ammonium nitrate is a highly oxidising material that poses an extremely high risk of explosion when combined with flammable substances. These substances are particularly critical, as they can immediately cause dangerous reactions if stored incorrectly or in the event of unintentional contact.

Example: Ammonium nitrate (LGK 5.1) and diesel. Under unfavourable circumstances, this combination can lead to a powerful explosion.

Organic peroxides and other chemicals

Organic peroxides are unstable compounds that decompose easily and release energy in the process. They often react explosively with other chemicals, especially with acids or metals.

Example: Acetone peroxide (LGK 5.2) and acids or metals. This mixture easily leads to self-decomposition of the peroxide, which can cause an explosion.

Explosive substances and flammable materials

Explosives and flammable chemicals are a particularly critical combination.

Explosive substances (e.g. nitroglycerine) should always be stored in isolation, as they can be detonated by mechanical impact or heat.

Storage in the immediate vicinity of flammable substances (such as petrol, alcohol or solvents) increases the risk of a small fire triggering a large explosion.

Toxic and non-toxic substances

Another important storage ban concerns toxic chemicals, which must not be stored together with non-hazardous substances. For example, food or drinking water could be contaminated by the vapours of toxic chemicals.  Spatial separation is therefore essential in laboratories and production facilities.

Pressurised gases and flammable substances

Pressurised gases such as propane or acetylene must be stored away from flammable substances. A leak or unintentional release can lead to explosive combustion. Safety valves and suitable storage conditions are crucial here.

Metal powder and water

Certain metal powders, such as magnesium or aluminium, react with water to form hydrogen gas. This gas is extremely flammable and can form explosive mixtures with air. Therefore, such metals must be stored in a dry place away from moisture.

What are the most important laws and regulations regarding the storage of chemicals?

In Germany, as an example, the safe storage of chemicals is subject to strict legal requirements, which are primarily regulated by the Technical Rules for Hazardous Substances (TRGS 510) and the Hazardous Substances Ordinance (GefStoffV).

TRGS 510: These technical rules specify detailed requirements for the storage of hazardous substances and define the conditions under which certain chemical substances may be stored. In particular, they regulate which substances are compatible with each other and can be stored together and which must be stored strictly separately.

This not only serves to prevent hazardous reactions, but also to reduce the risk of fire and explosion. In addition, TRGS 510 contains specifications on storage containers, ventilation systems and hazard prevention measures in the event of a chemical leak.

GefStoffV: The Hazardous Substances Ordinance forms the legal basis for the handling of hazardous substances in Germany. It defines which substances are classified as hazardous substances and contains detailed regulations on the labelling, packaging and storage of these substances. Companies are obliged to implement the protective measures specified in the Hazardous Substances Ordinance in order to protect both employees and the environment from the dangers of these substances.

These include the provision of safety data sheets, special training for employees as well as requirements for operational organisation and emergency measures.

REACH Regulation : In addition to these national regulations, companies in Europe must also comply with the European REACH Regulation (EC No. 1907/2006). REACH stands for ‘Registration, Evaluation, Authorisation and Restriction of Chemicals’ and is one of the most comprehensive chemicals regulations in the EU.

It obliges manufacturers, importers and downstream users to provide detailed information on the properties, hazards and safe use of their chemicals. The classification and labelling of chemicals in accordance with REACH is particularly relevant for storage, as it specifies which safety measures are required for certain substances. In addition, REACH contains regulations on the restriction or authorisation of certain substances of very high concern (SVHC), which impose strict requirements for their storage and use. Companies must ensure that they meet the requirements of the REACH regulation in order to guarantee legal compliance and minimise potential health and environmental risks from chemicals.

Valuable practical tips for safe storage

Implementing the safety regulations in practice requires attention and careful planning. A few basic measures that companies can take include

• Labelling and documentation: proper labelling of each chemical is crucial. All hazardous substances should be clearly labelled with the appropriate symbols and hazard warnings.
• Use of hazardous substance cabinets: Hazardous substance cabinets are specially designed to store hazardous substances safely. They provide protection against the spread of hazardous substances and prevent them from coming into contact with other chemicals.
• Temperature and humidity control: The correct storage temperature and humidity are often crucial to prevent unwanted reactions between substances. Regular monitoring is required here.
• Emergency measures: It is important that immediate emergency measures are taken in the event of incorrect storage. This includes equipping employees with suitable fire protection equipment and training them in the handling of hazardous substances.

Conclusion: The safe storage of chemicals is not only a legal obligation, but also a question of the company’s responsibility for the health of its employees and the safety of the company. Improper storage can lead to devastating consequences that can jeopardise the company, its employees and the environment. Companies should therefore ensure that they adhere to the relevant safety regulations and provide regular training on the correct storage of chemicals.

Compliance with regulations and the correct handling of hazardous substances play a key role in minimising the risk of accidents and ensuring the safety of employees. Safety awareness is essential in order to control the dangers of chemical storage and keep operations safe.