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Have you ever entered a building and were met with an overwhelming “good” smell? Usually, it is floral or citrus and intended to make the space smell good, clean and more appealing. In reality, this odor is an added volatile organic compound (VOC) and is diminishing the indoor air quality.

Fragrances in both air fresheners and cleaning supplies are often viewed as an indicator of cleanliness, especially in public areas. There is a perception that these smells indicate or imply good indoor air quality when it is doing the opposite. Instead, good indoor air quality is achieved by reducing sources, ensuring good ventilation and adding air cleaning when needed.

What causes these smells?

Odors are generally from volatile compounds in the air including volatile organic compounds (VOCs) but can also include inorganic gases like sulfur (rotten egg smell). Fragrances are often sprayed into the air where they are aerosolized (particles suspended into the air) and once suspended gases are released into the air.

Fragrances can be a wide range of compounds ranging from essential oils derived from plants to synthetic compounds. Cleaning supplies are often scented with compounds called terpenes that are naturally found in plants like lemon (limonene) and pine (pinene). Alone these compounds are not harmful but are easily reacted with ozone to decompose into other compounds like formaldehyde and ultrafine particles.

These aroma compounds in the air are then inhaled by occupants, some more irritating than others. This added chemical load can impact those who are sensitive or allergic to fragrances and can irritate medical conditions such as asthma.

Indoor Air Quality Standards

ASHRAE 62.1 is the industry standard for commercial building ventilation and acceptable indoor air quality (IAQ). Under ASHRAE 62.1 gas contaminants are minimized through source reduction, dilution by ventilation, and removal by air cleaners. LEED and WELL also emphasize proper ventilation, air filtration, and low-emission materials and reward buildings with low VOC concentrations.

Why are air fresheners a problem?

Diffusers, sprays and air fresheners do not remove odors but rather introduce a new contaminant source into the occupied space. If an IAQ assessment was conducted before and after implementation it would show an increase in VOC levels.

This increases the chemical load to the indoor environment and increases occupant exposure which can also lead to headaches, irritation, and occupant complaints.

There are many stories in the industry where engineers and building owners put in hours of work to meet LEED and/or ASHRAE 62.1 requirements only to fail the indoor air testing due to an added fragrance diffuser.

Mitigating Odors

When mitigating odors, the first step is to reduce or eliminate the sources. There is a wide range of odor sources both indoors and outside. Some include cleaning supplies, personal care products, kitchen exhaust, and building material and furnishings.

If odors continue after reducing sources, then air cleaning can help. There is a wide range of particulate and gas phase filtration options that can be used in HVAC systems that can target contaminants for a given application.

A perceived “good” scent is not an indicator of the indoor air quality. A building’s solution should align with industry experts including ASHRAE 62.1, LEED and WELL by removing contaminant sources, increasing ventilation where needed and adding air cleaning.