Fresh outdoor air is the foundation of every effective salon ventilation strategy. No amount of air filtration, recirculation, or purification can substitute for an adequate supply of clean outdoor air being brought into the salon. Outdoor air dilutes chemical vapours, replaces oxygen consumed by occupants, removes CO2 buildup, and carries away heat and moisture generated by salon operations. Salons that rely heavily on recirculated air — even with good filtration — create an environment where contaminant levels gradually climb throughout the day as the same air is cycled repeatedly through a chemically active space. Understanding how much outdoor air your salon needs, how to deliver it effectively, and how to maintain the systems that control it is a fundamental aspect of salon environmental management. This guide provides a practical diagnostic approach to evaluating and improving your salon's outdoor air supply.
Many salon HVAC systems are configured to minimise outdoor air intake. The reasons are understandable from an energy perspective — heating or cooling outdoor air is expensive, and minimising the outdoor air fraction reduces energy costs. However, the health trade-off is severe in a salon environment.
When a salon operates primarily on recirculated air, chemical vapours from each treatment accumulate progressively. The first colour service of the day releases VOCs that are partially removed by the HVAC filters. The second service adds more. By mid-afternoon, the background VOC level may be several times higher than the morning baseline, even though no single service produced a dramatic spike. CO2 levels follow a similar pattern — rising steadily as occupants consume oxygen and exhale carbon dioxide, with recirculated air providing no mechanism for CO2 removal.
This accumulation is insidious because it happens gradually. Staff who have been in the salon all day may not notice the declining air quality because their senses adapt to slowly increasing chemical concentrations. Clients arriving later in the day, however, may immediately notice the heavy, chemical-laden air that long-term occupants have become accustomed to.
CO2 itself, while not toxic at typical indoor levels, is a reliable indicator of ventilation adequacy. When CO2 exceeds 1,000 ppm — a common occurrence in under-ventilated salons — it signals that the space is not receiving enough fresh air for its occupancy level. Occupants in high-CO2 environments experience cognitive decline, fatigue, and difficulty concentrating, affecting both staff performance and client comfort.
The outdoor air problem is particularly acute in modern, well-sealed buildings. Older buildings with natural infiltration through gaps and cracks provided unintentional but often beneficial outdoor air exchange. Modern construction that minimises air leakage for energy efficiency creates tighter buildings that rely entirely on mechanical ventilation for outdoor air — and if the mechanical system is configured for minimal outdoor air, the result is a sealed box filling with contaminants.
Outdoor air intake requirements for commercial buildings are established through building codes, mechanical codes, and occupational health standards. These requirements set minimum outdoor air supply rates based on occupancy, floor area, and the type of activities conducted in the space.
ASHRAE Standard 62.1, widely referenced internationally, specifies outdoor air rates for different building types and occupancy categories. Beauty salons are typically classified as spaces requiring elevated ventilation due to the presence of chemical products. The standard calculates required outdoor air based on both occupancy (per-person rate) and floor area (per-square-metre rate), with the total being the sum of both components.
Most building codes adopt or reference ventilation standards similar to ASHRAE 62.1, establishing legally enforceable minimum outdoor air rates. These rates represent the minimum acceptable supply — salons performing extensive chemical services may need rates above the minimum to adequately control chemical exposure.
Occupational health regulations complement building codes by requiring that employers ensure adequate ventilation to control workplace hazards. Where chemical products are used, the duty to control airborne exposure effectively mandates outdoor air supply sufficient to dilute residual contaminants below occupational exposure limits.
Energy codes in many jurisdictions now include demand-controlled ventilation provisions that allow outdoor air rates to be adjusted based on occupancy sensors or CO2 monitoring. For salons, these provisions can be beneficial when properly implemented — increasing outdoor air during busy periods and reducing it during quiet times to balance air quality and energy efficiency.
Commissioning requirements in some jurisdictions mandate that HVAC systems be tested after installation to verify they deliver the specified outdoor air rates. Periodic recommissioning may also be required to ensure ongoing compliance as systems age and conditions change.
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Understanding your salon's outdoor air situation starts with understanding your overall ventilation picture. The MmowW free hygiene assessment tool evaluates your ventilation practices as part of a comprehensive hygiene assessment, helping you identify whether outdoor air supply is a gap in your salon's environmental management.
The assessment considers your HVAC setup, maintenance practices, and chemical handling procedures to provide a holistic view. Use the results as your starting point for the outdoor air improvements described below.
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Try it free →Step 1: Determine Your Current Outdoor Air Supply
Identify how outdoor air enters your salon. Check your HVAC unit for an outdoor air intake — this is typically a louvred opening on the exterior wall or roof connected to the air handler. Locate the outdoor air damper (the adjustable opening that controls how much outdoor air is mixed with recirculated air). Note the damper position — is it partially open, minimally open, or closed? If your HVAC system has no outdoor air intake, or if the damper has been closed to save energy, your salon is operating entirely on recirculated air plus whatever leaks in through the building envelope.
Step 2: Measure CO2 as a Ventilation Indicator
Install a CO2 monitor in the main salon area. CO2 levels directly indicate whether enough outdoor air is being supplied for the occupancy level. Target levels below 800 ppm for good air quality, with 1,000 ppm as the upper acceptable limit. If your CO2 readings consistently exceed 1,000 ppm during operating hours, your outdoor air supply is insufficient. Monitor for at least one full operating week to capture busy and quiet period patterns.
Step 3: Calculate Your Required Outdoor Air Rate
For a basic calculation, multiply the number of people typically in your salon (staff plus clients) by 10 litres per second per person (a common design rate for spaces with moderate contaminant sources). Add 1.2 litres per second per square metre of salon floor area. The total gives your approximate minimum outdoor air requirement in litres per second. Convert to cubic metres per hour by multiplying by 3.6. This calculation provides a reasonable estimate — your HVAC technician can refine it based on your specific conditions and applicable local codes.
Step 4: Adjust HVAC Outdoor Air Settings
Have your HVAC technician adjust the outdoor air damper to deliver at least your calculated minimum outdoor air rate. This may require rebalancing the system to maintain comfortable temperatures while delivering more outdoor air. In some cases, the existing HVAC system may not have the capacity to condition the increased outdoor air volume, requiring supplementary heating or cooling of the outdoor air stream.
Step 5: Address Air Distribution
Outdoor air must reach the people it is intended to protect. Verify that supply air vents are positioned to deliver fresh air to occupied zones — particularly the breathing zone of stylists at their workstations. Return air grilles should be positioned to draw contaminated air away from breathing zones toward exhaust points. Avoid short-circuiting where supply air flows directly to return grilles without mixing with room air.
Step 6: Consider Demand-Controlled Ventilation
For salons with variable occupancy, demand-controlled ventilation (DCV) optimises outdoor air supply based on actual need. CO2 sensors connected to the HVAC control system automatically increase outdoor air when occupancy rises and reduce it when the salon is quiet. This approach maintains good air quality during peak hours while reducing energy costs during off-peak periods.
Step 7: Maintain Outdoor Air Pathways
Regularly inspect outdoor air intakes for obstructions — bird nests, leaves, debris, snow, or building modifications that may restrict airflow. Ensure intake louvres and screens are clean and undamaged. Verify that outdoor air intakes are located away from contamination sources — exhaust outlets, loading docks, dumpsters, or traffic areas. Check that outdoor air damper actuators function correctly and respond to control signals.
Q: How much outdoor air does my salon need per person?
A: Most ventilation standards recommend between 8 and 15 litres per second of outdoor air per person for spaces like salons where chemical products are used. The specific rate depends on the services offered, the types of chemicals used, and the floor area per occupant. A salon with heavy chemical services such as keratin treatments and nail acrylics should target the higher end of this range. These rates are in addition to the per-area component, which accounts for contaminant sources beyond human occupancy. Your HVAC designer or technician can calculate the precise requirement based on your local code and salon-specific conditions.
Q: Does bringing in more outdoor air increase energy costs significantly?
A: Increasing outdoor air does increase the energy required to heat or cool the incoming air to comfortable levels. The impact varies by climate — it is most significant in extreme cold or hot climates and minimal in temperate conditions. However, the cost must be weighed against the alternatives — the health costs of inadequate ventilation, the potential regulatory consequences, and the productivity impact of poor air quality on staff and client experience. Energy recovery ventilators (ERVs) can reclaim energy from exhaust air to pre-condition incoming outdoor air, reducing the energy penalty by up to 70-80%. The investment in an ERV often pays for itself through reduced heating and cooling costs while maintaining high outdoor air supply.
Q: Can I use natural ventilation (windows) instead of mechanical outdoor air supply?
A: Natural ventilation through operable windows can supplement mechanical systems and is beneficial when conditions allow — mild weather, low outdoor pollution, acceptable noise levels, and adequate security. However, natural ventilation alone is unreliable as a primary outdoor air strategy for salons. Airflow through windows depends on wind direction, speed, and temperature differentials that vary constantly. In calm conditions, virtually no air exchange occurs through open windows. During extreme weather, windows must be closed for comfort, eliminating natural ventilation entirely. Most regulatory frameworks require mechanical ventilation in commercial premises where chemical substances are used, with natural ventilation considered a useful supplement rather than a primary control.
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