When a VOC Sensor Keeps Rising After Cleaning Products Are Used

When cleaning products are used, it is normal for a VOC sensor to rise for a period of time. The key question is whether the reading peaks and falls as the space is ventilated, or whether it keeps climbing, stays elevated, or appears in places and times that do not match the work being done.

For facility managers, commercial cleaners and mechanical contractors, the goal is to separate a temporary odour event from a broader indoor air quality issue that needs follow-up.

What a VOC sensor is actually showing

A VOC sensor measures changes in volatile organic compounds in the air, but it does not identify the exact chemical, product or source. It is a useful trend tool, especially when readings are compared before, during and after work in the same area.

That means a rising reading after cleaning does not automatically mean something is wrong. It may simply mean:

• •a product has been applied and is off-gassing as expected
• •airflow is not yet high enough to clear the area
• •the sensor is close to the source and is picking up a local plume
• •additional materials, such as adhesives, sealants or paint, are contributing to the reading

The important part is context. A sensor reading makes more sense when you know what work occurred, when it started, how long it ran, which products were used and whether the space was occupied or sealed during that time.

Common reasons a VOC reading keeps rising

A VOC reading that keeps increasing after cleaning can come from more than one source. In many buildings, the cause is not the cleaner itself, but a combination of work, ventilation and timing.

Cleaning and maintenance products

Some products release more VOCs than others, especially where strong odour cleaners, sprays, solvents, polishes or degreasers are used. Even when the product is used correctly, the sensor may continue rising for a while if the space is closed up or airflow is limited.

Other maintenance tasks can have a similar effect, including:

• •adhesive removal
• •touch-up painting
• •floor sealing or recoating
• •lubricant or spray application
• •carpet and upholstery treatment

Fit-out and refurbishment work

A fit-out can create a longer and more complex VOC pattern than routine cleaning. New joinery, flooring, paint, sealants, insulation and furnishings can all contribute to indoor air readings.

If a sensor keeps rising during a fit-out, ask whether the source is still active. Ongoing work, warm temperatures, or newly installed materials can keep emissions going for longer than expected.

Ventilation and air distribution issues

Sometimes the reading is not rising because emissions are increasing, but because the building is not clearing them effectively.

Check for:

• •supply air not reaching the affected area
• •return air paths being blocked
• •economiser or exhaust settings not matching the work
• •doors, partitions or temporary barriers changing airflow
• •localised pockets where air becomes trapped

If the space is being cleaned or worked on in a way that alters the air pattern, a VOC sensor near the source may stay elevated even after the product application has stopped.

How to tell whether the spike is temporary

A short VOC spike with a clear rise and fall is often consistent with recent cleaning or maintenance. A sensor that keeps rising, however, deserves a closer look.

Useful questions to ask are:

• •Did the reading start soon after a known product was used?
• •Has the work finished, or is it continuing nearby?
• •Is the sensor close to the source or in a different zone?
• •Has the air handling system changed settings?
• •Has the space been closed long enough for ventilation to work?

A practical approach is to compare the sensor trend with the work log. If the reading rises at the same time every day during cleaning, that pattern may be expected. If it rises long after the work is complete, or in areas where no products were used, the source may be elsewhere.

It can also help to check whether the odour matches the sensor reading. A strong smell is not proof of a serious problem, and a weak smell does not mean the air is clear. Sensors and odour are both clues, not a full diagnosis.

When to investigate further

Further investigation is sensible when the VOC trend does not settle after the work stops and the space has had a reasonable opportunity to ventilate.

Look more closely if:

• •the reading keeps climbing without any new product use
• •the same pattern appears in multiple areas that were not cleaned
• •the sensor stays elevated for longer than usual after the work finishes
• •people report strong or persistent odours that do not match the planned task
• •the space is newly fitted out and emissions seem to be coming from materials, not cleaners
• •the ventilation plant appears to be running, but the affected area is not clearing

In those cases, treat the sensor as a prompt to check sources, airflow and equipment rather than as a stand-alone answer.

What to check first

Start with the basics before assuming the sensor is faulty:

• •confirm the product name, Safety Data Sheet and application method
• •check whether nearby areas also used cleaning or maintenance products
• •review whether temporary barriers, film or furniture have changed airflow
• •look at the HVAC operating mode and whether outside air is being provided as intended
• •inspect the filter condition and pressure drop where gauges are fitted, in line with the equipment manufacturer’s instructions

If the building has been recently renovated or fitted out, the mechanical services engineer or building owner should confirm whether the ventilation arrangement is suitable for the space and the work being done. AS 1668.2:2024 may be relevant, but site requirements still need to be checked for the specific project.

Where filters fit into the picture

Air filters do not remove every gas or odour source on their own, but they are still part of the overall strategy. Filters capture particles, and in some systems activated carbon or similar media may be used to help manage certain airborne compounds, depending on the application.

If the issue is mainly VOCs from cleaning or fit-out work, the best response is often a combination of source control, ventilation and the right filtration arrangement for the system.

For facilities with frequent maintenance work or changing occupancy, it is worth checking whether the existing filter setup still suits the site conditions. If you need help selecting the right product, see our products or arrange filter servicing for support with inspection and replacement planning.

If you are measuring openings, frames or existing filters for a replacement, how to measure an air filter is a useful place to start.

A practical response plan for facilities teams

When a VOC sensor keeps rising after cleaning products are used, use a calm, step-by-step response:

• •confirm what work was done and what products were used
• •increase ventilation where safe and appropriate
• •check whether barriers, doors or temporary partitions are trapping air
• •compare readings across nearby areas, not just one sensor
• •inspect filters and pressure drop where the system provides that information
• •escalate to the mechanical services engineer if the pattern does not settle

This approach helps separate a normal short-term spike from a situation that needs further investigation.

For commercial cleaners, it also helps to label products clearly, record what was used and make sure the cleaning plan matches the ventilation available in the area. For contractors, it is worth considering how dust, adhesives and finishes will affect both odour and sensor readings during the job.

Talk to Total Air Filtration

Total Air Filtration is a family-owned air filter manufacturer and supplier based in Hillcrest, Brisbane QLD, and we work with facilities, cleaning teams and mechanical contractors across a wide range of sites.

If you need help matching the filter to the system, arranging a made-to-order solution, or checking what is suitable for your application, we can help with custom air filters and commercial filter servicing.

Call 07 3800 3448 or request a quote. If you need to get in touch directly, use contact us.