Plug-In Air Fresheners and VOC Monitor Limits

What a monitor can—and cannot—tell you

A consumer VOC monitor may show a higher reading while a plug-in air freshener is operating, but it usually cannot identify the chemicals present or prove that the freshener caused the change. These monitors are most useful for tracking patterns before, during, and after use—not for determining whether the air is safe.

Plug-in fresheners release fragrance ingredients and other compounds into the air. Some may register on a total volatile organic compound, or TVOC, sensor if they fall within its sensitivity range. Other airborne compounds may produce little or no response.

The U.S. Environmental Protection Agency explains that VOC sources, concentrations, and possible effects vary widely. A combined TVOC value does not show which individual compounds are present.

Which monitor readings may change?

• TVOC or eVOC: May respond to fragrance vapors, solvents, alcohols, cleaning products, cooking emissions, and many other sources. The displayed concentration is often an estimate based on the sensor’s response to a reference gas.
• Formaldehyde: A dedicated sensor may respond to formaldehyde, but some consumer sensors also react to other gases. Check the manufacturer’s documentation for cross-sensitivity and measurement limits.
• Particulate matter: A PM2.5 sensor measures airborne particles, not gases. A plug-in freshener may affect room odor or TVOC without changing PM readings.
• Carbon dioxide: A true CO2 sensor tracks carbon dioxide and can help indicate occupancy or ventilation patterns. It does not measure fragrance chemicals.
• Carbon monoxide: A carbon monoxide alarm is a life-safety device for detecting CO. It is not a VOC or fragrance monitor.

A low or unchanged TVOC reading does not confirm that no compounds were released. A high reading also does not identify the source, concentration of a specific chemical, or health significance.

Why TVOC readings can be difficult to interpret

Consumer VOC sensors can be affected by temperature, humidity, placement, calibration, sensor aging, and the mixture of gases in the room. Cooking, alcohol-based products, cleaners, paint, new furnishings, personal-care products, attached garages, and outdoor air can all change the result.

For that reason, there is no universal consumer TVOC number that separates acceptable from unacceptable indoor air. Alert bands shown by a monitor may be manufacturer-defined rather than regulatory health limits. Trends under similar conditions are generally more informative than a single reading.

How to check whether the freshener affects readings

1. Establish a baseline. Record the TVOC trend with the freshener unplugged and the room under its usual conditions.
2. Keep the monitor in one place. Position it in the occupied area according to its instructions, away from direct sunlight, supply vents, open windows, and the immediate plume above the freshener.
3. Change one factor. Operate the freshener as directed while avoiding cooking, cleaning, candles, sprays, and other likely VOC sources during the comparison.
4. Compare trends. Look for a repeatable rise during operation and a decline after the unit is unplugged. Do not rely on one short-lived spike.
5. Repeat the comparison. Testing on another day can help reveal whether temperature, humidity, ventilation, or an unrelated activity affected the first result.

This process can support a source-control decision, but it is not a laboratory chemical analysis. Identifying individual compounds requires compound-specific sampling and appropriate analytical methods.

Ways to reduce exposure

• Remove the source. Unplugging and discontinuing the product is the most direct way to reduce emissions associated with it.
• Use ventilation when appropriate. Bringing in outdoor air may dilute indoor pollutants, provided outdoor air quality and weather conditions are suitable. Kitchen and bathroom exhaust fans should vent outdoors to affect indoor air.
• Do not mask an underlying odor problem. Check for sources such as spoiled materials, damp items, trash, dirty drains, smoke residue, or inadequate housekeeping instead of relying only on fragrance.
• Avoid modifying the device. Do not refill, dilute, heat, or combine its contents, and follow the product’s use and disposal instructions.
• Choose filtration carefully. A standard particle filter, including HEPA media, does not remove gases by itself. Air cleaners with substantial activated carbon or other gas-phase media may capture some VOCs, but effectiveness varies by chemical, airflow, media quantity, and replacement condition. The EPA guide to air cleaners in the home explains the distinction between particle and gas removal.

If an odor or physical discomfort appears during use, stop using the freshener and air out the space when conditions allow. A consumer monitor should not be used to dismiss persistent symptoms or replace medical advice.

Related guides: VOC Monitor Limitations: Why “TVOC” Can Mislead • Where to Place an Air Quality Monitor: Height, Distance, and Rooms • Activated Carbon Filters Explained: VOCs, Odors, and What They Can’t Do

Frequently asked questions

Bottom line

A TVOC monitor can help reveal whether indoor gas readings repeatedly change when a plug-in air freshener operates, but it cannot identify the emitted chemicals or translate the result into a health verdict. Use the monitor for controlled comparisons, minimize competing sources, and prioritize source removal and appropriate ventilation when the goal is lower exposure.