Air duct cleaning in bakeries

Why is flour dust in bakery ducts a problem?

Flour that gets into the air ends up in extraction hoods, in ducts above dough machines and in the supply side of the ventilation. It builds up there. When a fan starts or the building vibrates, part of it comes loose again and settles in the work area. That way a duct becomes a second source of dust, even if you keep the floor clean every day.

The Health Council's advice concerns sensitisation: according to the advice, 0.2 mg/m3 of inhalable wheat flour dust over 8 hours corresponds to an additional risk of 1 percent of becoming hypersensitive. For comparison: in Belgium the sector fund Alimento uses a limit of 0.5 mg/m3 for flour dust over 8 hours. Those figures are not a requirement for your ducts, but they make clear that every cloud of dust counts.

Where flour collects

• Extraction hoods above mixers and kneaders.
• Horizontal duct sections, where dust settles and stays.
• Bends and reducers, where the air velocity drops.
• Grilles and valves in the shop next to the bakery.

Flour dust extraction cleaning: the basic rules

The sector is clear about this. Alimento calls compressed air, hand brushes and brooms a definite no and advises an industrial vacuum cleaner with HEPA. TNO writes in a memo for the bakery sector that you no longer use compressed air for cleaning but a vacuum cleaner, for which an M class filter is sufficient. In EX zones, according to TNO, an industrial vacuum cleaner with ATEX 114 certification is essential.

The key point: the duct is under negative pressure while you clean. Everything the brush loosens goes straight into the extraction. The components for this are listed under duct sealing balloon for cleaning contractors.

ATEX and explosion risk in bakery ventilation ducts

Flour, meal and sugar are combustible substances. According to the TNO memo, a dust explosion is only possible above 60 g/m3 of fine dust in the air. You will not reach that during normal work in a bakery, but you can in an enclosed space where a thick layer of dust is suddenly blown up. A duct or extraction cabinet is exactly that kind of space.

That is why any cleaning job should fit within your explosion protection document. If you have designated EX zones, that classification determines which equipment you may use there. An ordinary 230 volt machine is not automatically suitable for such a zone.

Checklist before you start

1. Check in your explosion protection document whether the duct or cabinet falls within an EX zone.
2. Remove coarse dust first with a suitable industrial vacuum cleaner.
3. Switch off the ventilation and lock it so it cannot be switched on.
4. Seal off the section and apply negative pressure.
5. Use equipment that is permitted in the zone concerned.

Not sure which version is suitable for your zone? Ask Lamers for advice on the right machine before you order. Besides duct cleaners, Lamers also supplies industrial vacuum cleaners.

Which equipment should you choose for bakery extraction duct cleaning?

Bakeries often have a mix of short, small ducts at the hoods and longer runs to the roof. That determines the choice.

• Small bakery, short ducts: PD4 duct cleaner for cleaning contractors is driven by a power drill on battery or mains and has a shaft of 2.5 to 7.5 metres. Handy for the small ducts at hoods and grilles.
• Larger bakery or long runs: the DC4 duct cleaner for cleaning contractors reaches up to 30 metres and cleans ducts of 100 to 600 mm, including vertical runs and 90 degree bends.
• Brushes: flour is light and dry, so a soft or standard brush is often enough. Caked deposits with grease and moisture sometimes need a more aggressive Tynex brush. Read how to approach duct cleaning brushes for cleaning contractors.

Compressed air cleaning is not a first choice in a bakery, given the advice not to use compressed air. If you still want to work with a compressed air nozzle in a fully sealed duct under negative pressure, discuss it first with your prevention officer and record it in your work instruction.

An overview of all machines and sets is on the page where you can duct cleaning kit for cleaning contractors.

Fictional example: a craft bakery with a shop

A bakery has a production room with two kneaders and an oven, and next to it a shop with its own ventilation. The baker notices a fine white layer forming on the shelves in the shop, even though the door between bakery and shop is usually closed.

An inspection shows that the extraction above the kneaders and the extract from the shop join in one duct to the roof. Because of contamination, the resistance in the bakery section has increased, so that air carrying flour partly flows back through the shop section. The solution has two parts: clean the duct under negative pressure and have the installer check the air balance.

What this example shows: complaints in the shop can have their cause in the bakery. The principle that air must not flow from dirty to clean applies here too. Larger companies will find that principle worked out under air hygiene in the food sector.

How often should ventilation ducts in a bakery be cleaned?

There is no statutory frequency for bakery ducts. What is established: under article 6.2 of the Working Conditions Decree (Arbobesluit), an employer must ensure sufficient uncontaminated air and the installation must always be in working order. A duct full of flour does not help with that.

Does your business also fry or grill? Then grease is added to the mix. Other points of attention apply there, which you will find under cooker hood duct cleaning. More background on intervals is available under how often should air ducts be cleaned.

A simple way to make this work in practice is to add the duct checks to the cleaning schedule you already keep for the production room. Write down who looks, when, and what they saw, so that a gradual build up of flour is noticed long before it becomes a problem.