Fully synthetic metalworking fluids

Theory

The difference between an emulsion and a solution is structural rather than gradual: in an emulsion a second liquid phase is present as fine droplets, in a solution that phase boundary no longer exists. Much of what follows on this page originates there. It does not follow automatically, though: how strongly each point makes itself felt is decided by the specific formulation, not by membership of a product class. Anyone reading this page as a list of class properties will be surprised by the first real application.

The classification, done properly

The governing terminology standard is the German DIN 51385:2013-12, “Lubricants. Processing media for forming and machining of materials. Terms”. One detail that is regularly overlooked: the umbrella term “metalworking fluids” was replaced there by “processing media”, and “metalworking fluids” now refers only to the media used in material-removal processes. Because the older umbrella term is established in industry, it continues to be used, here too.

The first split is between non-water-miscible and water-miscible metalworking fluids. Non-water-miscible products are used undiluted. Water-miscible products are concentrates that are diluted with water to working strength before use; the result of that dilution is called a water-mixed metalworking fluid. The three terms are not interchangeable: the concentrate in the drum is water-miscible, the fluid in the tank is water-mixed.

Within the water-miscible products, DIN 51385 distinguishes two types: emulsifiable fluids, which form an oil-in-water emulsion with water, and water-soluble fluids, which form colloidal or true solutions with water. The second type is what the market calls fully synthetic. The intermediate step sold as semi-synthetic or micro-emulsifiable sits between the two: a very fine, translucent oil-in-water dispersion.

This is where precision pays. “Fully synthetic”, “semi-synthetic” and “part-synthetic” are market terms, not designations defined in any standard. Neither the German DGUV Rule 109-003 nor the metalworking fluid portal of the IFA, the institute for occupational safety of the German statutory accident insurance, uses them in its definitions. When writing an enquiry, therefore, do not ask for “fully synthetic” but for water-soluble and mineral oil free. That is the property actually meant, and unlike the market term it can be verified.

Internationally, ISO 6743-7 assigns processing media to family M within lubricant class L; the MHx codes designate the non-water-miscible products and the MAx codes the water-miscible ones.

Ask for the property, not the label: “water-soluble, mineral oil free” can be verified, whereas “fully synthetic” is a marketing description with no standardised content.

Why a solution is clear

A macro-emulsion scatters visible light because its oil droplets are large enough to do so; it looks milky. Once the droplets become much smaller than the wavelength of visible light, scattering falls off sharply and the micro-emulsion turns translucent. A true solution has no phase boundary left at which light could be scattered: its constituents are dissolved molecularly or ionically. It is clear. Colloidal solutions, which DIN 51385 expressly includes, may show slight opalescence, so “clear” is the normal case rather than the definition.

In practice this means you can see through the sump to the cutting edge, the tank floor, the chips and the pump. Tramp oil, suspended solids, biofilms and deposits show up earlier. That is a process advantage because it buys diagnostic time and not because a clear sump is inherently better than a cloudy one.

What does the lubricating when there is no oil

In an emulsion the oil phase supplies the lubricating film. In a solution the additives do. The German DGUV Rule 109-003 lists the additive groups used in metalworking fluids: film-forming substances, extreme-pressure additives for boundary lubrication at high contact temperatures, corrosion inhibitors, antioxidants, anti-mist agents, defoamers, surface-active substances, dispersants, emulsifiers, solubilisers and biocides.

The mechanism is therefore essentially boundary lubrication: polar molecules adsorb onto the metal surface and form a separating layer there; water-soluble polymers increase the tenacity of the entrained film; the additives for extreme-pressure lubrication in turn build boundary layers, partly by physical adsorption and partly as tribochemically formed reaction layers on the metal surface freshly generated in the cut. How much such a layer carries follows from the interplay of additive chemistry, contact pressure, temperature and surface condition, not from a switching threshold: adsorptive additives already contribute at moderate conditions, while more strongly reactive systems typically develop their effect under higher loads. What is missing is a reservoir of oil that can be drawn in under load. That is exactly where the load limit discussed below comes from.

Heat removal and a widespread false expectation

The cooling capacity of a water-mixed metalworking fluid comes overwhelmingly from the water, whose specific heat capacity is roughly twice that of mineral oil. At normal working concentrations the concentrate changes little about that. The difference between emulsion and solution therefore lies not in heat capacity but in heat transfer at the hot surface: a fluid with lower interfacial tension wets better and reaches the place where the heat is generated.

Anyone expecting “more cooling” from a changeover should therefore pin that expectation on the delivery system rather than on the product. Thermal drift of dimensions is primarily a question of fluid delivery and temperature control; the fundamentals are on the Metalworking page.

Wetting, flushing, drag-out: one variable, three signs

Water-soluble products are frequently formulated for low interfacial tension because that improves wetting. It is not a class characteristic: how heavily surface-active substances and polymers are dosed is a matter of the formulation, and a low-surfactant water-soluble fluid behaves differently from a surfactant-rich one. Where interfacial tension really is low, however, it works in three directions at once:

• positive: better wetting, better penetration into the contact zone, better flushing, cleaner chips and workpieces;
• negative: a greater tendency to foam, because the same surface-active substances stabilise entrained air; how much depends on surfactant type, defoamer and water hardness;
• negative: more drag-out, because a well-wetting film clings to the part and to the chip and leaves the machine with them.

Buy the first point and you generally buy the other two with it. That is not a defect of the product type but a boundary condition to be handled in the plant: through defoaming, delivery pressure, drop heights in the return line, chip drainage sections and the top-up regime. Which sign predominates in a given case is shown by a trial in production, not by a data sheet.

Basis: DIN 51385:2013-12 (terminology; the non-water-miscible / water-miscible / water-mixed split and the emulsifiable / water-soluble split); DGUV Rule 109-003 “Activities involving metalworking fluids”, April 2026 edition, section 2 (definitions) and no. 1 (additive groups); IFA metalworking fluid portal, “Types of metalworking fluid” (accessed 09 August 2026); ISO 6743-7:1986 (confirmed 2020). The formation of boundary layers by additives for extreme-pressure lubrication is deliberately worded against the widespread short version: adsorption and tribochemical reaction run alongside one another, and there is no single activation temperature.

On the shop floor

The most common mistake in a changeover is to swap the product and leave the plant as it is. The advantage of a solution only materialises once the peripheral equipment can collect it; its drawbacks appear precisely where that equipment cannot.

Where water-soluble fluids play to their strengths

Grinding processes come first. The material removed appears as a very fine grinding sludge, which in an emulsion limits filterability and sump life. Because a solution contains no dispersed oil phase that could be retained in the filter medium or sheared in the pump, finer filtration is usually possible. That does not make it unlimited: polymers, surface-active substances and corrosion inhibitors can adsorb onto or be removed by the filter medium, and the sump is then depleted of exactly the constituents that carry it. Filter fineness, filter medium and sump life therefore have to be set together with the supplier and re-checked after the changeover against reserve alkalinity and corrosion behaviour, not read off a data sheet.

Other good fits are processes with high cleanliness requirements on the part, processes with optical monitoring inside the working area, processes with long sump life, and central systems serving many machines.

Plant engineering is not an accessory

Filter fineness and filter medium have to match the material removed; chip conveyors need a drainage section; tank volume and residence time have to be sufficient for settling and de-aeration; the return line should avoid free fall; tramp oil separation has to be able to do the job it can do in a solution; and extraction has to match the aerosol actually generated. For plant design the German DGUV Rule 109-003 refers explicitly to VDI 3035 Part 1, and for maintenance in service to VDI 3397 Part 2; the processing media themselves are covered by VDI 3397 Part 1 in its 2020-03 edition. We deliberately give no filter finenesses, tank volumes or residence times here: for this product type we have no citable, generally valid design figures, and dimensioning belongs with the plant supplier and the VDI guideline.

Tramp oil behaves differently, with consequences for measurement

Slideway, hydraulic and spindle oil find their way into every sump. In an emulsion part of it is taken up by the emulsifier system. In a solution the capacity to take up an oil phase is fundamentally lower, so tramp oil tends to separate out on the surface and can be skimmed. That, too, is not automatic: where a formulation carries plenty of surface-active substances it can emulsify tramp oil as well, in which case it stays in the sump, the skimmer runs dry and turbidity increases even though there is “supposed to be” a solution in the tank. Whether separation works in your plant is shown by how much the skimmer actually collects during the first weeks; that is a measurement, not an assumption.

For monitoring this has a documented consequence: determining concentration with a hand refractometer gives false readings where tramp oil is present, whereas determining reserve alkalinity by acid titration is independent of tramp oil. Both methods also need a product-specific correction factor; the refractometer factor and the titration factor are therefore separate header fields in the model test plan of the DGUV Rule. The two methods are complementary and do not replace one another, and a factor carried over from a previous product is simply wrong.

Mixing and make-up water

Even for a solution the order stands: put the water in first, then stir in the concentrate slowly. The make-up water is an operating material with requirements of its own. Under the German TRGS 611 the nitrate content of the make-up water must not exceed 50 mg/l; otherwise it has to be corrected with demineralised water. Drinking water quality is recommended. Water hardness is a separate point: soft water increases the tendency to foam where the product contains anionic surfactants, because the hardness salts that would otherwise partly deactivate them through the formation of insoluble lime soaps are absent.

Basis: DGUV Rule 109-003, April 2026 edition, section 3.2 (reference to VDI 3035 Part 1), section 6.2.2 (mixing), section 7.1.1 (reference to VDI 3397 Part 2, make-up water) and Annexes 3a and 3b (test methods, refractometer and titration factor); VDI 3397 Part 1:2020-03 (processing media); TRGS 611, May 2007 edition, no. 5.2 (nitrate in make-up water). Statements on filterability and tramp oil separation are deliberately conditional: they depend on formulation, filter technology and plant operation and are not properties of the product class.

What it is worth

The honest version first: the benefit of a water-soluble fluid is rarely “better lubrication”. It nearly always sits in four other places, and one of them comes with a caveat.

Sump life and disposal volume

Where a sump manages without a mineral oil phase and can be filtered more finely, it may last longer for the same standard of care. That then pays twice: fewer fresh charges and less waste fluid. Longer sump life is not, however, promised here, and it is not a property of the product class. Micro-organisms do not live on mineral oil alone; they metabolise esters, glycols, surface-active substances and whatever else is carried in. Whether a changeover extends sump life depends on the maintenance regime, tramp oil ingress, make-up water, filtration and machine downtime, and has to be measured in service.

The treatment routes that shrink or fall away when there is less waste fluid are named in section 8 of DGUV Rule 109-003: chemical splitting, membrane filtration and thermal splitting. One point that must not be overlooked: non-ferrous metal inhibitors such as benzotriazole and tolyltriazole are a subject in their own right during waste treatment.

Downstream cleaning effort

Anyone who has to wash, bond, paint, coat or weld a part after machining pays for every oil film applied beforehand. Whether that saves a washing stage in a particular case is decided by the downstream process chain and not by a data sheet. The residue left by a dried-out solution is not an oil film, but it is not nothing either (see Risks).

Downtime

Blocked filters, clogged nozzles, failed pumps and biofilms in pipework are downtime. The DGUV Rule lists blocked lines, filters and pumps explicitly as an indication of heavy microbial contamination. A clear sump makes such developments visible before they stop the machine. That is the real value of being able to see through it: not aesthetics, but lead time.

Consumption, with a caveat

Here the benefit is expressly qualified. Better wetting means more drag-out, and drag-out is consumption. Whether a changeover lowers or raises concentrate consumption depends on the drainage section, on chip geometry and on whether top-up is done with water or with ready-mixed fluid. Anyone building a business case has to measure this item rather than estimate it.

What will not appear in such a calculation are percentages from us. We have no substantiated figures for gains in sump life or reductions in consumption, and we therefore quote none. Any percentage claim about savings would have to come from a documented trial of your own, and then with a baseline, a comparison object, test conditions and a date.

Basis: DGUV Rule 109-003, April 2026 edition, sections 8.1.1 to 8.1.3 (treatment routes), section 8.2 (non-ferrous metal inhibitors in treatment), section 7.1.1 (indications of microbial contamination). We hold no substantiated figures on sump life or consumption gains, and therefore quote none.

Risks

The risks of this product type are not product weaknesses but limits of the principle and boundary conditions of the plant. Know them and the changeover works; skip them and you will look for the problem in the wrong place afterwards. The most uncomfortable point is deliberately placed in the middle rather than at the end.

The load limit

Where there is no reservoir of oil to be drawn in under load, the load-carrying capacity of the film has to come entirely from the additive package. Where that package is not designed for it, the film thins out under high specific load; the symptoms are built-up edge, flank wear and surface defects. Experience shows heavy roughing and peeling cuts, deep-hole drilling, thread forming, broaching and tough high-alloy materials to be the critical cases.

That implies no blanket exclusion. There are water-soluble fluids with pronounced lubricating properties that carry demanding operations, and there are emulsions that fail at the same point. Suitability does not follow from the product class but from workpiece material, operation, delivery technique and additive package. It is settled by a specific release trial on your own part, not by the designation on the container. The classification of the processes is on the Metalworking page.

Materials: aluminium, non-ferrous metals, ductile iron

Aluminium is amphoteric and is attacked by alkaline media. Water-mixed metalworking fluids are predominantly run on the alkaline side, among other things for corrosion protection. How far into the alkaline range is a question of the individual formulation, not of the product class. Where the setting is unsuitable for the material, staining, discoloration and tarnishing follow, particularly where wet parts dwell for longer and with aluminium casting alloys. Release for a specific material therefore has to be established product by product.

With non-ferrous metals, copper ions go into solution in an alkaline aqueous medium; this produces copper salts, discoloration on brass and, via the dissolved ions, an additional load on the sump. The technical answer is non-ferrous metal inhibitors; the DGUV Rule names benzotriazole and tolyltriazole.

One risk that comes with every water-mixed metalworking fluid and still has to be known: chips and dust from ductile iron or certain magnesium alloys can form phosphine on contact with water, with a garlic-like odour. Containers holding accumulations of chips or dust are the critical case; they are to be removed from the working area regularly and in good time.

Foam

Foam is the most common start-up problem after a changeover, and in most cases the cause does not lie in the product. Three sources, in the order in which they should be checked: first, surfactant residues from the system cleaning; the DGUV Rule states unambiguously that the circuit should be rinsed thoroughly after using cleaning agents and system cleaners, because residual surfactant contents lead to heavy foaming; second, soft make-up water, where the product contains anionic surfactants; third, mechanical air entrainment through high delivery pressure, free fall in the return line and the pump.

That a water-soluble fluid “foams more” than an emulsion is not a rule but an observation that depends on surfactant type and defoamer system. It serves as a check after a changeover, not as a statement about the class.

We could not identify a standardised foam test applicable to water-mixed metalworking fluids; in practice testing is done in-house. This page therefore claims no test standard for foam.

Skin, airways, nitrosamines: where “mineral oil free” is most often misread

The nitrosamine rules continue to apply. In Germany, DGUV Rule 109-003 requires in section 4.4.1 that only water-miscible or water-mixed metalworking fluids complying with TRGS 611 are used, with no exemption for mineral-oil-free or fully synthetic products. N-nitrosamines form from nitrosatable secondary amines and nitrite; whether mineral oil is in the formulation is irrelevant to that reaction. The limits set by TRGS 611: secondary amines as a constituent are not permitted, and from impurities at most 0.2 % by mass relative to the concentrate; nitrite above 20 mg/l in the water-mixed fluid calls for a change, a partial change or the addition of an inhibitor in consultation with the manufacturer; N-nitrosodiethanolamine at most 5 mg/kg and N-nitrosomorpholine at most 1 mg/kg; for the sum of carcinogenic N-nitrosamines in air, 0.2 µg/m³ is regarded as the state of the art.

A note for readers outside Germany: TRGS 611 and DGUV Rule 109-003 are German rules and are binding for operations in Germany. Elsewhere your own national occupational safety framework applies. The chemistry does not change with the jurisdiction, and neither does the practical consequence: nitrite monitoring, pH control and documentation remain the sensible minimum wherever water-mixed fluids containing amines are run.

The skin is loaded differently, not automatically less. TRGS 611 requires skin contact to be limited to the unavoidable minimum and refers to TRGS 401 for that purpose. DGUV Rule 109-003 devotes a separate section 6.6 to skin protection, including the prohibition on wearing protective gloves when working on moving machine parts, tools and workpieces. Whether a particular fluid loads the skin more or less follows neither from the oil basis nor from the product class, but from the specific formulation together with concentration, sump life, microbial load, tramp oil ingress and contact time. That assessment has to be made in the plant; it cannot be derived from the words “mineral oil free”, and we do not pre-empt it.

And air monitoring becomes more laborious, not less. It is worth keeping three things apart that are regularly conflated in practice:

• There is no occupational exposure limit for “metalworking fluids”. The German TRGS 900 contains no such entry. Anyone quoting one is quoting something that does not exist.
• The figure of 5 mg/m³ is substance-related, not product-related. TRGS 900 lists it for “mineral oils (petroleum), highly refined” as the sum of vapour and aerosol. It applies where that substance is present in the air. It cannot be transferred to mineral-oil-free systems. Not because it would be too strict or too lenient, but because the substance it applies to is not there.
• The figure of 8 mg/m³ is an exposure limitation value, not an occupational exposure limit. DGUV Rule 109-003 gives it in its April 2026 edition for water-mixed metalworking fluids in metalworking, again as the sum of vapour and aerosol. It is expressly not derived on health grounds: even where it is complied with, health risks to employees cannot be ruled out.

For this product type one further sentence settles the matter: for metalworking fluids that are not mineral-oil based, no suitable summation measurement methods are currently available, so exposure has to be assessed solely via the individual ingredients. In practice that means there is no single measurement to hold against a summation value. Instead the relevant ingredients have to be identified (the safety data sheet is the starting point) and each assessed against the criterion that applies to it, following the methodology of TRGS 402 or its national equivalent. That is more work, not less. Anyone moving to a mineral-oil-free fluid should settle this point with their occupational safety specialist before the changeover rather than after it.

“Mineral oil free” is a statement about composition. It is not a statement about skin loading, not one about aerosol formation, and not one about the effort of the risk assessment; for air monitoring the effort is demonstrably higher.

Micro-organisms

No mineral oil does not mean sterile. Micro-organisms live on surfactants, esters, glycols and whatever is carried in. The DGUV Rule names the following as indications of heavy microbial contamination: a fall in reserve alkalinity, a marked drop in pH, foaming, a rise in nitrite concentration, instability, unpleasant odour, discoloration, visible biofilms or floating biomass, and blocked lines, filters and pumps. There is no obligation to monitor microbiology; in central systems it is nevertheless sensible. The relevant guidance is DGUV Information 209-051, “Microbial contamination of water-mixed metalworking fluids”.

Residues, paint, elastomers

When a solution dries out it leaves no oil film but a salt-like, polymeric or soap-like residue. On slideways, in collets, on sensors and in guarding it can feel tacky or varnish-like. It can usually be redissolved with water (which an emulsion residue does not offer), but it is there. Equally, glycols, glycol ethers and amines can attack certain paints, seals and viewing panels. Both have to be checked case by case and must not be assumed; we hold no citable source giving specific material pairings, which is why this page says “check” rather than “is compatible”.

Basis: DGUV Rule 109-003, April 2026 edition, section 4.3 (no summation measurement methods for fluids that are not mineral-oil based), section 4.4.1 (requirement to comply with TRGS 611), section 5.1.2 (phosphine), section 5.1.2.1 with Table 1 (exposure limitation value of 8 mg/m³, expressly not derived on health grounds), section 6.2.1 (surfactant residues), section 6.6.3 (gloves), section 7.1.1 (indications of microbial contamination), section 8.2 (non-ferrous metal inhibitors); TRGS 611, May 2007 edition, nos. 4.2, 5.3 and 5.4 (amines, nitrite, nitrosamines) and no. 5 (skin contact, reference to TRGS 401); TRGS 900, version of 05 June 2026 (substance-related occupational exposure limit for highly refined mineral oils as the sum of vapour and aerosol; it contains no entry for metalworking fluids); TRGS 402, September 2023 edition (substance-by-substance assessment of inhalation exposure); DGUV Information 209-051, July 2016.

Testing and changeover

The complete testing and monitoring plan is on the Metalworking page. It applies to every water-mixed metalworking fluid and belongs there because that is where a maintenance engineer looks for it: daily visual inspection, weekly pH and nitrite, nitrate in the make-up water, colony counts as required, and documentation of every biocide addition. The governing documents are Annexes 3a and 3b of DGUV Rule 109-003 together with TRGS 611.

Set out here are only the four figures that behave differently with a water-soluble solution than with an emulsion. The intervals refer to continuous operation and may differ under other operating conditions.

All measurements are to be documented; TRGS 611 requires this expressly of the employer, and the DGUV Rule governs documentation and retention in section 7.4.

Before the changeover: the compatibility plan

Most disappointing changeovers are not product failures but skipped preparation. The following seven points belong before the order, not after the first shift. Deliberately without figures: filter finenesses, residence times and material pairings cannot be stated in a generally valid way, but the questions to ask can, and so can the place that can answer them.

The changeover is a cleaning job

Top up only, and what you get is not a water-soluble sump but an undefined mixture of residual emulsion, tramp oil, established micro-organisms and new concentrate, with foam, turbidity, inexplicable refractometer readings and a sump life worse than its predecessor's. Annex 4 of DGUV Rule 109-003 sets out a model cleaning plan for circuits carrying water-mixed metalworking fluids that works as a procedure:

1. Remove deposits where possible, for example fungal growth and biofilms.
2. Add a system cleaner to the circulating old charge before the change and circulate it. The dosage and circulation time are given in the model cleaning plan; the supplier's instructions apply in addition.
3. Drain the fluid; clean tank, lines and machine mechanically.
4. Rinse with diluted fluid.
5. Drain, then hose out, rinse out and vacuum tank and machine.
6. Send spent fluid and rinsing liquid for disposal or treatment.
7. Refill the plant immediately afterwards with a fresh charge.
8. Take a sample and determine concentration, pH and nitrite; these are the baseline values against which everything later is measured.

The instruction most often skipped is in the same annex: for corrosion reasons the plant is not to be left standing empty, even briefly. Heavily fouled plants additionally call for extended mechanical methods (brushing, steam jetting, high-pressure water flushing, pulse flushing) and possibly a biocide addition on refilling. Where aerosols are generated, respiratory protection is to be worn, and chemical protective gloves when handling the media. System cleaners and biocide concentrates may only be used by persons who have been instructed and assigned to do so, and system cleaners must not contain or form substances that conflict with the substance restrictions.

The first weeks: what you release the changeover against

In the first weeks after the first fill, test more closely than in continuous operation: the sump picks up tramp oil, hardness salts and micro-organisms that the cleaning did not reach. If something shows up in this phase, four causes are equally in play: the plant, the make-up water, the cleaning that preceded the fill, and the formulation itself. Which one applies is settled by measurement, not by expectation. None of the four is exonerated in advance, including the fluid supplied. They can only be told apart if it is settled before the fill which finding speaks for which cause and which result counts as acceptance. It is therefore worth agreeing with the supplier in writing, before the fill, which figures will be watched and which finding triggers which decision:

• Record the baseline. Concentration, pH and nitrite immediately after the first fill, together with the refractometer and titration factors and the hardness and origin of the make-up water. Without that line no later reading can be judged.
• Concentration within the band agreed with the supplier, measured with the product-specific factor and cross-checked against reserve alkalinity.
• pH trend with no sustained downward movement; the trend across several measurements is the statement, not the daily reading.
• Nitrite below the trigger value; where TRGS 611 applies, the response to exceeding it is prescribed and not negotiable.
• Skimmer yield actually present; it is the proof that tramp oil separates in your plant rather than being emulsified.
• Filter life and foaming against the previous state, each recorded together with whatever else was changed on the plant at the same time.
• Corrosion behaviour on a reference part under the conditions that actually occur, intermediate storage included.
• Feedback from the operators on skin and odour. That is not a soft factor but an early finding, and part of the risk assessment.
• A control mix outside the plant. A mix from the same container with water of known hardness, made up in a drum and carried alongside. If it shows the same picture as the sump, that points to the formulation or the water; if it does not, that points to the plant or the cleaning. Without this control, any attribution of cause remains an assertion.

Release the changeover when these figures stay stable over a period agreed in advance and not when the first shift has run without incident.

Basis: DGUV Rule 109-003, April 2026 edition, Annexes 3a and 3b (test plan, methods, header fields), Annex 4 (model cleaning plan, extended methods, protective measures), section 6.1.7 and section 7.1.5 (system cleaners), section 7.4 (documentation and retention); TRGS 611, May 2007 edition, nos. 5.2, 5.3 and 5.5 (make-up water, nitrite, test intervals, duty to document); TRGS 402, September 2023 edition (methodology for inhalation exposure). Figures from DGUV Rule 109-003 are quoted here only where they are independently substantiated. The compatibility plan deliberately gives no filter finenesses, residence times or material pairings: for this product type we hold no citable, generally valid design figures; dimensioning belongs with the plant supplier and VDI 3035 Part 1.

Rules and standards

Rules and standards are revised, withdrawn and replaced. The table below gives, for each document, the edition this article relies on and what it is used for here. Most of these documents are German: TRGS are Technical Rules for Hazardous Substances issued under the German Hazardous Substances Ordinance (GefStoffV), and DGUV rules and information sheets are published by the German statutory accident insurance. They are binding for operations in Germany; readers elsewhere should read them as a well-documented state of the art alongside their own national framework. Where a document is substantiated only indirectly via another, that is stated.

Not a substitute for your risk assessment. This article describes the general state of the art and the applicable body of rules. It does not replace the risk assessment required under section 6 of the German Hazardous Substances Ordinance (GefStoffV) and TRGS 400, nor the operating instructions, staff instruction, or any product-specific approval. For each product, the current safety data sheet and technical data sheet prevail, together with the arrangements in force at your site. Responsibility for selection, operating conditions, monitoring and documentation rests with the employer.