What are volatile organic compounds (VOCs) and how can buildings manage them?

Key points

• Volatile organic compounds (VOCs) are gases released from many everyday materials and activities inside buildings.
• Common indoor VOC sources include paints, adhesives, furnishings, cleaning products, printers, cooking, and some building materials.
• VOCs vary widely in behaviour and risk. “VOCs” is a broad category, not a single pollutant.
• Ventilation, source control, material selection, and targeted air cleaning all play roles in VOC management.
• Particle filters such as HEPA filters are not designed to remove gases effectively on their own.
• Gas-phase filtration technologies such as activated carbon and catalytic filters are commonly used to reduce VOC concentrations indoors.

Indoor air discussions often focus on particles such as PM₂.₅, dust, or smoke. However, many indoor air quality problems are driven by gases rather than particles. One of the broadest categories of indoor gases is volatile organic compounds (VOCs).

This article explains what VOCs are, where they come from, why they matter in buildings, and how ventilation and air cleaning strategies can help manage them.

What are VOCs?

VOCs are carbon-containing chemicals that easily evaporate into the air at room temperature.

The term “volatile” refers to how readily the compound becomes a gas. Many VOCs are emitted continuously from materials and products used inside buildings.

Examples of VOCs include:

• formaldehyde
• benzene
• toluene
• xylene
• ethanol
• acetone
• limonene

Some VOCs are naturally occurring, whilst others are synthetic industrial chemicals.

Importantly, VOCs are not one single pollutant. Different VOCs behave differently in terms of:

• odour
• persistence
• chemical reactivity
• health relevance
• interaction with other pollutants

That is why broad statements such as “removes VOCs” should always be interpreted carefully.

Where do VOCs come from indoors?

Indoor VOCs can originate from a surprisingly wide range of sources.

Common building-related VOC sources include:

Building and furnishing materials

• paints and varnishes
• sealants and adhesives
• composite wood products
• flooring materials
• insulation products
• furniture and soft furnishings

Occupant activities

• cooking
• cleaning
• use of fragrances and air fresheners
• smoking or vaping
• hobbies and crafts
• use of solvents

Office and commercial environments

• printers and copiers
• cleaning chemicals
• stored products and packaging
• renovation activities

Outdoor sources entering indoors

Outdoor VOCs can also enter buildings through ventilation and infiltration, especially near:

• traffic
• industrial activity
• fuel combustion sources

Indoor VOC concentrations are often influenced by a combination of indoor generation and outdoor air quality.

Why do VOCs matter in buildings?

VOCs matter because they can influence:

• perceived air freshness
• odours
• occupant comfort
• indoor chemistry
• overall indoor air quality management

Some VOCs are relatively low concern at typical indoor concentrations. Others may require closer attention depending on concentration, exposure duration, and the specific compound involved.

One challenge is that indoor environments rarely contain just one VOC. Real buildings contain complex mixtures that change over time depending on occupancy, activities, temperature, and ventilation patterns.

Certain VOCs can also react indoors to form secondary pollutants.

For example, some VOCs react with ozone to form additional airborne by-products, including fine particles and reactive compounds. This is one reason why understanding secondary air pollution matters when evaluating air cleaning technologies.

What is TVOC?

You may see measurements reported as TVOC (total volatile organic compounds).

TVOC is a broad indicator representing the combined concentration of many VOCs detected by a sensor or test method.

However, TVOC has limitations:

• it does not identify individual chemicals
• different sensors respond differently
• not all VOCs are equally important
• two spaces with the same TVOC may have very different chemical profiles

TVOC can still be useful for trend monitoring, identifying changes, or detecting unusual indoor pollution events. But it should not be treated as a complete description of indoor air chemistry.

How are VOCs measured?

VOC assessment methods vary widely depending on the objective.

Real-time sensors

Low-cost VOC sensors are often used in:

• smart building systems
• indoor air quality monitors
• building management dashboards

These are useful for trends and comparative monitoring, but they are usually not compound-specific.

Laboratory sampling

More detailed VOC analysis may involve:

• sorbent tube sampling
• canister sampling
• gas chromatography/mass spectrometry (GC/MS)

These methods can identify individual VOCs and provide much more detailed information about indoor air composition.

How can buildings manage VOCs?

There is rarely one single solution for VOC control. Effective management usually combines several approaches.

1) Source control

The most effective VOC reduction strategy is often reducing emissions at the source.

This can include:

• selecting lower-emission materials
• isolating strong emission sources
• controlling chemical storage
• choosing lower-VOC cleaning products
• allowing off-gassing periods after renovations

In many cases, removing or reducing the source is more effective than trying to clean the air afterwards.

2) Ventilation

Ventilation dilutes indoor VOC concentrations by introducing outdoor air.

This is one reason ventilation remains essential in building design and operation. Guidance from organisations such as CIBSE treats ventilation as a core component of indoor environmental quality.

However, ventilation has limitations:

• outdoor air may itself contain pollutants
• energy use increases when conditioning outdoor air
• some buildings cannot easily increase airflow rates
• outdoor pollution events may reduce the benefit of ventilation

Because of this, many buildings combine ventilation with air cleaning strategies.

3) Gas-phase air cleaning

Particle filtration and gas filtration are not the same thing.

HEPA filters are highly effective for particles, but they are not designed to remove gases efficiently.

VOC reduction typically requires gas-phase filtration technologies such as:

• activated carbon
• impregnated sorbents
• chemisorption media
• catalytic oxidation systems

Different technologies target different chemical classes and concentrations.

For example:

• activated carbon is widely used for broad VOC adsorption
• catalytic systems aim to chemically transform certain gases into less harmful compounds

This is why understanding how indoor air purification technologies work matters when comparing systems.

4) Combining filtration approaches

Real indoor environments usually contain both particles and gases.

For that reason, many commercial and healthcare-focused air cleaning systems combine:

• particulate filtration (such as HEPA)
• gas/VOC filtration
• catalytic technologies

This layered approach reflects the fact that no single technology addresses every indoor pollutant equally well.

Why VOC claims should be interpreted carefully

VOC performance claims can sometimes sound broader than the underlying evidence.

When reviewing claims, it helps to ask:

• Which VOCs were tested?
• At what concentration?
• Under what conditions?
• Was the testing performed in a chamber or a real room?
• What was the exposure duration?
• Were any by-products evaluated?

This is especially important because gas-phase filtration performance often changes over time as filter media becomes loaded or saturated.

For more on interpreting performance data, see:

• How should you read laboratory test reports for air purifiers?
• What does “log reduction” mean in air cleaning performance claims?

VOCs, ventilation, and building strategy

VOC management is ultimately a building systems question rather than a single-device question.

Good outcomes usually depend on combining:

• sensible material selection
• appropriate ventilation
• pollutant-aware operation
• targeted air cleaning where needed
• monitoring and maintenance

Different buildings face different VOC challenges:

• offices may focus on furnishings and occupancy
• healthcare settings may involve cleaning agents and disinfectants
• schools may experience intermittent high occupancy and cleaning cycles
• homes may be affected by cooking, renovations, and consumer products

The right strategy depends on the pollutant sources, occupancy patterns, and operational constraints of the space.

Summary

VOCs are airborne chemicals released from many materials, products, and activities inside buildings. Because VOCs are gases rather than particles, they require different management approaches.

Ventilation remains an essential tool for dilution, but ventilation alone is not always sufficient or efficient. Source control, material selection, and gas-phase air cleaning technologies can also play important roles.

For building operators and occupants, the key point is that “indoor air quality” is not just about dust or particles. Understanding gases and VOCs is equally important when designing healthier and more resilient indoor environments.