SDS Section 9: Physical Properties That Change Risk

SDS Section 9 lists physical and chemical properties of a substance or mixture. These facts can help a COSHH assessor understand why a task releases vapour, dust or mist, and why storage or spill controls matter. The section is a source of product information, not a ready-made decision about risk in your workplace.

Why does physical form matter to a COSHH assessment?

A product's form influences how it may reach people. Powder can become airborne during tipping, a liquid can splash, and a spray process can create mist even when the supplied product was a liquid. The Health and Safety Executive (HSE) asks COSHH assessors to consider dust, fume, vapour, mist and gas produced by work, as well as skin contact with liquids, pastes and dusts.

Start with the form as supplied, then describe what the task does to it. Heating can increase vapour release; cutting or grinding can produce dust from a solid; spraying can create aerosol. Section 9 may help explain behaviour, but observation and process knowledge are needed to assess the released form. The same product can have different exposure routes in two activities.

Physical state also affects containment. A stable bottle tray may work for a liquid leak but do little for airborne powder released at head height. A work method should prevent release at source rather than assuming a generic spill kit can manage every form.

Which properties are useful for planning controls?

Depending on the product, Section 9 may include appearance, pH, boiling or flash point, vapour pressure, solubility and other relevant properties. The REACH safety data sheet structure sets out the section's role. Values need interpretation in the conditions of actual use; a property measured under one condition may not describe a heated or mixed process.

Vapour pressure and boiling information can help explain whether vapour release is plausible. pH may matter to handling and splash risk, although it does not replace the product's classification or first-aid instructions. Solubility can affect containment and clean-up planning. Flash point informs flammability assessment, which may also require consideration under DSEAR. Do not make a definitive control decision from one number without reading the rest of the SDS and the task.

Be careful with “not available” and “not applicable”. They are not synonyms for “safe”. Some mixture sheets provide broad ranges or omit a value for a valid reason; the assessor may need clarification from the supplier. Record uncertainty rather than filling it with a guessed number.

How should Section 9 be read with other SDS sections?

Section 2 summarises classified hazards. Section 7 gives handling and storage advice. Section 8 addresses exposure controls. Section 10 covers stability and reactivity. Section 9 helps make those recommendations intelligible. For example, a volatile liquid's handling advice may call for containment and ventilation; a reactive material's storage conditions may depend on temperature or moisture.

HSE says an SDS provides information to help make a workplace assessment and is not itself that assessment. Use the exact product identity and current revision. A value copied from another supplier's formulation may be misleading, even if the product name is similar.

Connect properties to the process: temperature reached, quantity open, transfer method, ventilation, people nearby and release duration. A table can help document that link: property, task implication, control and evidence. Avoid repeating every Section 9 line in the COSHH record without explaining why it matters.

What should change when a property changes?

If a supplier revises Section 9, compare the changed value with the activities using that product. A new or corrected volatility, pH or physical-state detail may affect exposure, storage or spill response. Review controls and train users on any changed method. If the product formulation changed, also confirm container identity and stock rotation.

The Safe Foundry feature overview shows how SDS and assessment records can stay linked, while the assessment workflow adds task context. The goal is to use the property to answer a practical question: what could be released here, who could encounter it and which control prevents that route?

What would a property-to-control table show?

For a liquid transfer task, a reviewer might list physical state, relevant volatility information, pH and any flammability property from the exact SDS. Beside each value they write the task condition: room temperature or heated, closed pump or open pour, amount handled and who stands nearby. The next column states the control decision, such as closed transfer, splash protection or separate fire-risk review. A final column records uncertainty and who will resolve it.

This structure stops Section 9 from becoming a copied list of values. A number only matters when connected to a credible release or condition. It also helps avoid overinterpreting a property. A flash point can inform a DSEAR question, but it does not alone decide whether the work area is safe. A pH value may prompt a closer look at skin and eye hazards, but it does not replace classification and first aid information.

How do process changes alter the meaning of a value?

Suppose the same liquid is first wiped on a surface and later sprayed. The Section 9 properties did not change, but the airborne form did. A vapour pressure value cannot describe all the mist generated by atomisation. Similarly, a solid that is stable in a block may create dust when sanded. The COSHH record should describe what the process produces, not only what the supplier delivered.

Heating, cooling, dilution and mixing can also change behaviour. A property on a supplier sheet may apply to the supplied mixture, not a new in-house mixture. Seek competent advice where the changed state affects control, and do not invent a new property by interpolation. The more the process changes the material, the less a single original SDS can answer on its own.

What if the data is a range or absent?

Ranges can be appropriate for mixtures, but they may be too broad for a particular engineering decision. Ask whether the worst credible part of the range changes the control choice. If so, seek supplier clarification or competent technical assessment. Record why a conservative assumption was used, rather than presenting it as measured fact.

When a field says “not available”, separate missing data from a negative result. A blank flash point is not evidence that a product cannot burn; a blank solubility field is not a spill plan. Compare other SDS sections and seek more information where the task depends on it. Preserve the question in the review record until it is resolved.

Finally, check consistency. If Section 7 calls for cool storage but Section 9 lacks the property you expected, that may be normal or may merit a supplier question. The task owner need not become a chemist, but they should recognise when the source does not support a confident workplace decision.

When one Section 9 value drives an equipment choice, record that link explicitly. A future supplier revision can then trigger a targeted review of the affected pump, ventilation or storage condition. Otherwise, a changed PDF may be filed without anyone noticing that the original control assumption has moved.

Ask the task owner to confirm the property still describes the product and conditions in use, especially after dilution, heating or a formulation change.