Can good housekeeping reduce a Zone 22 to a non-hazardous area?

Partly. Good housekeeping can remove the Zone 22 that exists only because settled dust could be raised into a cloud, provided the cleaning is reliable, documented and checked. It cannot remove Zone 22 caused by secondary releases from the plant itself, such as leaking joints or a torn filter, and it does nothing to Zone 20 or Zone 21 created by the process.

Short answer

• Zone 22 usually has two causes: secondary-grade releases from equipment, and layers of dust that a disturbance could lift. Housekeeping acts only on the second.
• IEC 60079-10-2 builds the housekeeping level into the classification. At the "good" level, layers are kept negligible or absent whatever the grade of release, so they add no zone.
• HSE guidance for inspectors (rubber and plastics industries) accepts an adjacent room with no dust release of its own as unclassified if it is kept permanently clean and its door is kept closed.
• Releases from leaks are reduced by fixing the plant: tight joints, extraction at the source, negative pressure, maintained filters.
• The cleaning regime becomes part of the basis of safety. If it lapses, the classification is wrong and the equipment in the area may no longer be suitable.

What housekeeping can and cannot change

Area classification starts from the sources of release. Housekeeping does not change how often a flange leaks or a filter element fails; it changes whether the dust that escapes is allowed to accumulate. That is the dividing line.

IEC 60079-10-2 states that its examples assume effective housekeeping that prevents layers from accumulating; where housekeeping is not effective, clouds raised from layers must be added to the classification. The Irish Health and Safety Authority (HSA) summarises the three housekeeping levels of the 2015 edition: good (layers negligible or non-existent, irrespective of the grade of release, so the risk of clouds and fires from layers is removed), fair (layers not negligible but short-lived, typically less than one shift, removed before a fire can start) and poor (layers not negligible and persisting, typically more than one shift, with possibly significant fire and secondary explosion risk). Only the good level removes layers as a source of clouds.

What "good housekeeping" has to mean

A zone drawing that relies on cleaning is only as good as the cleaning. To support a reduction, the housekeeping must be a system, not an intention:

• Prevent first. Directive 1999/92/EC puts preventing the formation of explosive atmospheres at the top of the order of measures. The HSA guide pairs good housekeeping with well-designed dust extraction wherever dust is likely to be released; cleaning that removes the same layer every day is a sign of a leak to fix.
• Set the frequency from the accumulation rate. The interval must keep layers negligible between cleans, including after spills and upsets, not only on average.
• Include high surfaces. HSE guidance for inspectors stresses high-level ledges, beams and light fittings: if dust dislodged from them could form a large cloud, the whole room is Zone 22.
• Use methods that do not raise clouds. HSE recommends vacuum systems and advises against compressed air lines for dislodging deposits.
• Write it down and check it. Method, frequency, responsibility and the inspection record belong in the explosion protection document with the zone drawing, so that an auditor can see that the assumption still holds.

The third edition of IEC 60079-10-2 (2026) also contains a subclause on a zone of negligible extent (Zone NE). Its criteria are in the standard and are not public; do not assume that a clean room automatically qualifies.

Worked example: a store next to a bagging hall

A bagging hall is Zone 22 throughout, with Zone 21 at the filling spouts. The adjacent store is also drawn as Zone 22 because dust drifts through an open doorway and settles on pallets and racking.

The plant fits a self-closing door, improves the extraction hood at the spouts and vacuums the store daily, including the racking tops, with a weekly recorded inspection of high surfaces. The store has no dust release of its own. After a trial period shows no measurable layers, it can be reclassified as non-hazardous, in line with the HSE example of an adjacent room that is permanently clean with the door kept closed. The bagging hall itself keeps its Zone 21 at the spouts and Zone 22 around the conveyor flexible connections, because those are releases from the plant that cleaning does not stop.

The reclassification also changes what equipment may be installed in the store. If the cleaning later lapses, ordinary equipment would be sitting in a dust atmosphere it was never assessed for, so the review and audit of housekeeping must continue for as long as the reduced classification is used.

Common mistakes

• Reclassifying on paper. A new drawing without a changed cleaning routine, measured results and a responsible person does not make the area safe.
• Ignoring the sources. Housekeeping cannot remove Zone 22 around leaking flanges, flexible connections or the clean side of a filter.
• Cleaning with compressed air. It raises exactly the cloud the classification assumes will not occur.
• Checking only the floor. Layers on beams, cable trays and above suspended ceilings are often the deciding factor.

Related on excodex

• Dust zones 20, 21 and 22 explained with practical examples
• Dust layers and housekeeping: how thick is too thick?
• Does a dust layer create a zone, or only a dust cloud?
• Can compressed air be used to clean combustible dust?
• Standards spaces: IEC 60079-10-2, ATEX 1999/92/EC

Standards and further reading

• IEC 60079-10-2:2026 (edition 3.0, June 2026, replaces the 2015 edition), classification of areas for explosive dust atmospheres, including layers as a source of release, the zone of negligible extent (Zone NE) and informative Annex C on levels of housekeeping: preview (ANSI webstore)
• Directive 1999/92/EC, Article 3 (order of prevention and protection measures) and Annex I (zones; layers, deposits and heaps as sources): Article 3, Annex I
• Health and Safety Authority (Ireland), ATEX delivery guide, combustible dust (housekeeping levels): hsa.ie
• HSE, area classification for explosible dusts in the rubber and plastics industries (guidance for inspectors): hse.gov.uk
• HSE, HSG103 Safe handling of combustible dusts (housekeeping and cleaning methods): hse.gov.uk (PDF)
• IEC Common Data Dictionary, housekeeping level "poor": electropedia.org

This article is general technical information prepared by the excodex editorial team. It does not replace the applicable standards, the equipment certificates and instructions, national regulations or the assessment of a competent person.