In brief
The Regulation on the Protection of Buildings from Fire divides combustible and flammable liquids into classes according to flash point and prohibits storing them in work areas, corridors and escape routes. Liquids such as thinners and solvents are kept at the workbench only in the quantity needed for the shift; the rest is kept in a fire-resistant cabinet, an isolated area or a separate store. During transfer, no liquid is transferred until equipotential bonding and earthing have been set up between the containers.
Why is flammable liquid storage subject to separate rules?
Thinner on the paint line, solvent in the maintenance workshop, diesel for the generator or acetone in the laboratory: they all raise the same question. At what temperature can this liquid's vapour ignite, and how much of it can be kept in the workplace, and where? Flammable liquid storage rules are the answer to these two questions. The main source of the rules is the fourth section of the Regulation on the Protection of Buildings from Fire (BYKHY) (Arts. 113–123).
On the OHS side, two documents come into play: the explosion protection document for areas where flammable vapour may form, and the risk assessment of chemicals. This article focuses on storage and transfer rules; for zone classification, see our article on ATEX and the explosion protection document.
What is flash point, and how are the classes determined?
The flash point is the lowest temperature at which a liquid forms enough vapour at its surface to ignite. If the flash point is below room temperature, the liquid gives off ignitable vapour even while standing in an open container. BYKHY Art. 113 classifies liquids as follows:
| Class | Definition (BYKHY Art. 113) | Typical examples |
|---|---|---|
| IA (flammable) | Flash point below 22.8 °C, boiling point below 37.8 °C | Diethyl ether |
| IB (flammable) | Flash point below 22.8 °C, boiling point 37.8 °C or above | Acetone, ethanol, toluene, most cellulose thinners |
| IC (flammable) | Flash point between 22.8 °C and 37.8 °C | Xylene |
| II (combustible) | Flash point between 37.8 °C and 60 °C | Diesel |
| IIIA (combustible) | Flash point between 60 °C and 93 °C | Some heavy solvents and fuels |
| IIIB (combustible) | Flash point 93 °C and above | Most hydraulic and machine oils |
The examples are a guide; take your own product's flash point from section 9 of the safety data sheet. The regulation gives one more warning: Class II and IIIA liquids heated above their flash point are treated as Class I. A heated oil bath or diesel standing near a hot surface is more dangerous than its class on paper.
Daily quantity in the production area: how much thinner can stay at the workbench?
BYKHY Art. 115/1 is clear: flammable and combustible liquids cannot be stored in corridors, passageways, on and under stair landings, in basements, on escape routes and in work areas. On the other hand, Art. 123 excludes from the scope of this section the processing of a liquid in production or keeping it briefly as an intermediate product. When you read the two together, the practical rule emerges: at the workbench there is use, not storage.
Apply thinner storage rules in the production area on site as follows:
- Calculate the shift's needs. On a paint line using an average of 12 litres of thinner a day, keep a few hours' need next to the line, not the whole day's stock.
- Use suitable containers. Instead of an open bucket, a cut-off plastic bottle or an unlabelled drum, prefer a lidded, labelled metal safety can, preferably with a spring-loaded lid and flame arrester.
- Do not forget used rags. Rags and cotton waste soaked in solvent are collected in a lidded metal waste bin and removed from the area at the end of the shift.
- Put it back at the end of the shift. The remaining liquid goes back to the cabinet or store; no liquid stays at the workbench overnight.
- Keep ignition sources away. Welding, grinding and work requiring an open flame are only done under a hot work permit.
Flammables cabinet: how much, and how?
Under BYKHY Art. 115/2, in buildings where ancillary work is carried out and which are separated from other areas of use by walls and floors with at least 90 minutes' fire resistance, the following quantities can be stored in a storage room or in a cabinet with 10 minutes' fire resistance at 200 °C:
- Class IA liquids: 100 litres in the original container
- Class IB, IC, II and IIIA liquids: a total of 500 litres in original containers
- The same classes in portable tanks: a total of 2,500 litres
For liquids stored together with Class I liquids, the calculation is made under Art. 114/3: 5 litres of Class II or IIIA liquid is counted as equivalent to 1 litre of Class I liquid.
Flammables cabinets on the market are usually classified by fire resistance time under the EN 14470-1 standard (with types such as 15, 30, 60 or 90 minutes). When choosing and using a cabinet, check the following:
- Do the doors close and lock by themselves; are they wedged open?
- Is there a sump in the base to collect leaks, and is it clean inside?
- Have the ventilation connection and earthing specified by the manufacturer been made?
- Have oxidisers, acids and toxic substances been put in the same cabinet? Incompatible chemicals are kept apart; for details, see our article on chemical storage compatibility.
- Is the cabinet in front of an escape route or exit door?
Solvent storage: isolated areas and separate stores
There are two options for quantities exceeding the cabinet capacity. The first is a storage area inside the factory building where the liquid is processed, isolated from the area where the process is carried out (Art. 118/3). The quantity permitted here depends, according to the Annex 12/B table of the regulation, on the size of the area, its fire resistance and whether there is automatic extinguishing:
| Storage area (maximum) | Fire resistance | Extinguishing system | Permitted quantity |
|---|---|---|---|
| 15 m² | 60 minutes | None | 70 litres/m² |
| 15 m² | 60 minutes | Present | 175 litres/m² |
| 50 m² | 120 minutes | None | 140 litres/m² |
| 50 m² | 120 minutes | Present | 350 litres/m² |
The second option is a separate store building. The main requirements of Art. 118 are:
- The store building is built with at least 120 minutes' fire resistance; the doors also have at least 120 minutes' resistance.
- A building where Class I liquids are stored has no basement; Class II liquids cannot be stored in a basement.
- The floor is made of liquid-tight and non-combustible material; spilled liquid is prevented from reaching channels and drains.
- If natural ventilation is not enough, explosion- and spark-proof mechanical ventilation effective at floor level and providing at least 6 air changes per hour is installed.
- The store building cannot adjoin dwellings or spaces where people are present; entry by those with no business there is prohibited by a sign.
- The store volume is hazard zone 1; the area within a 5-metre radius of doors, windows and openings, up to a height of 0.8 metres above the floor, is hazard zone 2.
Earthing and equipotential bonding during transfer
In every transfer from drum to can, or from can to spray gun, a static charge builds up as the liquid flows. If there is a potential difference between the containers, a spark can occur and ignite the vapour of a liquid with a low flash point. BYKHY Art. 122/4 requires tanks and the parts of the installation conductively connected to them to be installed so that they carry no voltage to earth, and earthing connection points to be easily accessible and secured against loosening. Apply the same logic to drum and can transfers with the following steps:
- Connection first, then the lid. A clamped equipotential cable is attached between the emptying drum and the container being filled, and the drum is also connected to an earthing point. The connection is made before the lid is opened, and removed after the transfer has finished and the lid has been closed.
- Prefer metal containers. Standard plastic cans cannot be earthed; use conductive containers when transferring flammable liquids.
- Fill without splashing. Keep the filling hose close to the bottom of the container, do not let the liquid fall freely from above and keep the flow slow.
- Use a suitable pump. Instead of tipping the drum, use a hand pump suitable for flammable liquids or an explosion-proof pump.
- Check. Visually check that clamps and cables are sound before transfer; the earthing installation is included in the annual periodic inspection together with the internal electrical installation, and you can track its date with the OHS calendar tool. For details, see our article on earthing and residual current devices.
Spills and fire preparedness
Even the best storage arrangement is tested one day by a can that tips over. There should be a spill kit (absorbent material, a lidded waste container, gloves and goggles) next to storage and transfer points; use our article on chemical spill response for the response steps. The extinguisher is chosen according to the type of liquid: BYKHY Art. 122 lists in particular foam, carbon dioxide, dry chemical powder and water for flammable liquids. You can find which extinguisher is used where in our article on types of fire extinguisher.
In businesses that use chemicals, plastics and paints, we incorporate the storage arrangements into the risk assessment and prepare employees to use extinguishers in a real fire scenario. In our fire training service, we deliver theoretical and hands-on training. For other risks specific to the sector, see our chemicals and plastics page.
Frequently Asked Questions
What is flash point?
It is the lowest temperature at which a liquid forms enough vapour at its surface to ignite. The BYKHY treats liquids with a flash point below 37.8 °C as flammable (Class I), and those at or above this temperature as combustible (Classes II and III). Your product's value is in section 9 of the safety data sheet.
Can I keep thinner in the production area?
For use, yes; for storage, no. Flammable liquids cannot be stored in work areas; at the workbench there is only as much thinner as the shift needs, in a lidded and labelled container. The remaining quantity goes back to the flammables cabinet or store at the end of the shift.
How many litres of liquid can be put in a flammables cabinet?
In buildings meeting the conditions in BYKHY Art. 115/2, 100 litres of Class IA liquids and a total of 500 litres of Class IB, IC, II and IIIA liquids in original containers can be stored in a cabinet with 10 minutes' fire resistance at 200 °C. Also, do not exceed the capacity stated by the cabinet manufacturer.
Can flammable liquids be transferred in a plastic can?
Because standard plastic containers cannot be earthed, conductive metal containers and equipotential bonding should be preferred for transferring flammable liquids. Cables are attached before the transfer, the liquid is filled without splashing and there are no ignition sources nearby.
Fire classes, choosing the right extinguisher, hands-on extinguishing in a safe open area and an evacuation drill, all in one training.
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.