Indoor carbon dioxide (CO₂) levels have long been used as a shorthand for indoor air quality (IAQ) and ventilation performance—but new guidance from ASHRAE (approved February 12, 2025) offers a more nuanced take. If you’re an HVAC professional, building designer, or facilities manager, this update could reshape how you monitor and manage indoor environments.

In this post, we’ll unpack what ASHRAE’s updated position means, why it matters, and how you can align with best practices going forward.
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ASHRAE has officially clarified that CO₂ is not a reliable, all-purpose indicator of indoor air quality. That’s a major shift in perception for many professionals and organizations that have relied on CO₂ levels as a go-to metric.
Here’s what’s changing:

• CO₂ can help evaluate ventilation but shouldn’t be treated as a standalone measure of IAQ.
• Health effects linked to typical indoor CO₂ levels are inconsistent and don’t justify changes to ventilation standards—yet.
• Consumer-grade CO₂ sensors can mislead if not properly calibrated or positioned.
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Historically, CO₂ levels have been used to infer whether a room is "stuffy" or under-ventilated. But ASHRAE’s 2025 position document emphasizes this can be dangerously simplistic.
While rising CO₂ concentrations may correlate with increasing levels of other indoor pollutants (because they all rise in poorly ventilated spaces), CO₂ is not the pollutant to worry about. In fact:

• Many indoor pollutants, like volatile organic compounds (VOCs) and particulates, aren't emitted in correlation with CO₂.
• Removing CO₂ alone does not improve overall air quality.

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ASHRAE's revised position includes several critical recommendations for research and practice:
1. Use CO₂ Only as a Supplemental Tool - CO₂ can still help assess outdoor air ventilation rates—but only if applied correctly, with validated assumptions and proper sensor placement.
2. Avoid Over-Reliance on CO₂ for Infection Control - CO₂ is often promoted as a proxy for airborne virus risk, but its relationship to disease transmission is complex and indirect. Infection risk also depends on occupancy patterns, space types, filtration systems, and more.
3. Do Not Use CO₂ to Justify Air Cleaning Alone - Technologies that remove only CO₂ may interfere with ventilation controls and give a false sense of safety about indoor air quality.​

If you work in HVAC, construction, education, healthcare, or real estate, here’s how to adapt:

• Calibrate CO₂ sensors regularly and ensure proper placement.
• Use CO₂ alongside other IAQ indicators—not in isolation.
• Educate clients and stakeholders about the limitations of CO₂ as a ventilation metric.
• Stay current with ASHRAE Standard 62.1, which now includes updated CO₂ setpoints for DCV—not as health limits, but for operational guidance.

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​As outdoor CO₂ levels continue to rise due to global climate change, indoor readings will shift as well. This reality makes it more important than ever to distinguish between indoor-generated CO₂ and ambient levels, especially when fine-tuning ventilation systems.
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ASHRAE’s new position on indoor CO₂ is a call for smarter, more holistic air quality management. By understanding the limitations of CO₂ as an IAQ metric—and by investing in comprehensive, evidence-based monitoring—you can make better decisions for occupant health, safety, and performance.

In today’s world, creating safe, healthy, and sustainable buildings is more important than ever. Whether you're a building owner, facility manager, or an industrial hygienist, understanding the various building standards available can help you make informed decisions that benefit both occupants and the environment. Four key frameworks that guide building design and operation are WELL, LEED, ASHRAE, and the Alberta Infrastructure Guidelines. Each of these standards has a unique focus and offers distinct benefits. Let’s explore the differences and advantages of each.
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The WELL Building Standard is a performance-based system that focuses on the health and well-being of building occupants. It is designed to enhance human health through building design, operation, and behavior.
Key Focus Areas:

• Air Quality: WELL emphasizes maintaining clean indoor air by reducing pollutants like particulate matter (PM2.5, PM10), volatile organic compounds (VOCs), and carbon dioxide (CO2).
• Water Quality: Ensures access to clean and safe drinking water.
• Light: Promotes exposure to natural light and circadian lighting design to improve sleep and productivity.
• Comfort: Focuses on thermal, acoustic, and ergonomic comfort to enhance occupant well-being.
• Mind: Encourages mental health initiatives, such as biophilic design and stress-reduction spaces.

Benefits:

• Health and Well-being: WELL-certified buildings prioritize occupant health, leading to improved productivity, reduced absenteeism, and enhanced mental well-being.
• Employee Satisfaction: Companies that invest in WELL certification often see higher employee satisfaction and retention rates.
• Market Differentiation: WELL certification is a mark of leadership in health-focused building design, setting your building apart from others.

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LEED is one of the most widely recognized green building certification systems in the world. It focuses on sustainability across various aspects of building design, construction, and operation.
Key Focus Areas:

• Energy Efficiency: LEED encourages the use of energy-efficient systems and renewable energy sources.
• Water Conservation: Promotes water-saving technologies and practices.
• Materials and Resources: Encourages the use of sustainable, non-toxic materials and waste reduction strategies.
• Indoor Environmental Quality: Focuses on improving air quality, lighting, and thermal comfort for occupants.

Benefits:

• Environmental Impact: LEED-certified buildings reduce their carbon footprint, conserve water, and minimize waste, contributing to global sustainability efforts.
• Cost Savings: LEED buildings often have lower operating costs due to energy and water efficiency measures.
• Increased Property Value: LEED certification can increase a building’s market value and attract environmentally conscious tenants or buyers.

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ASHRAE provides technical standards and guidelines primarily focused on HVAC (heating, ventilation, and air conditioning) systems and energy efficiency. ASHRAE standards are widely adopted in building codes and are essential for ensuring safe and efficient building operations.
Key Standards:

• ASHRAE 62.1: Ventilation for Acceptable Indoor Air Quality, which sets minimum ventilation rates to ensure good indoor air quality.
• ASHRAE 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings, which provides minimum energy efficiency requirements.
• ASHRAE 55: Thermal Environmental Conditions for Human Occupancy, which defines acceptable thermal comfort ranges for occupants.

Benefits:

• Improved Indoor Air Quality: By following ASHRAE 62.1, buildings can ensure proper ventilation and reduce indoor pollutants, leading to healthier environments.
• Energy Efficiency: ASHRAE 90.1 helps buildings optimize energy use, reducing operational costs and environmental impact.
• Regulatory Compliance: Many building codes require adherence to ASHRAE standards, making them essential for compliance with local regulations.

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The Alberta Infrastructure Guidelines are specific to government-owned and supported infrastructure in Alberta, Canada. These guidelines ensure that public buildings meet safety, functionality, and sustainability requirements.
Key Focus Areas:

• Safety and Functionality: Ensures that public buildings are safe for occupants and meet functional requirements for their intended use.
• Sustainability: Encourages the use of energy-efficient systems and sustainable building materials.
• Indoor Air Quality: Provides specific guidance on maintaining good IAQ through proper ventilation, pollutant control, and regular maintenance.

Benefits:

• Compliance with Provincial Regulations: Following these guidelines ensures that public sector projects (including schools)  in Alberta meet local regulatory requirements.
• Enhanced Public Safety: The guidelines prioritize occupant safety, ensuring that public buildings are safe and healthy for all users.
• Sustainability Goals: By incorporating energy-efficient systems and sustainable practices, the guidelines help align public buildings with Alberta’s sustainability goals.

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While all four frameworks aim to improve building performance, they each have a unique focus:

• WELL: Prioritizes occupant health and well-being, making it ideal for workplaces and residential buildings focused on human-centric design.
• LEED: Offers a comprehensive approach to sustainability, suitable for projects aiming to minimize environmental impact and enhance building performance.
• ASHRAE: Provides technical standards for HVAC systems and energy efficiency, essential for optimizing building systems and ensuring regulatory compliance.
• Alberta Infrastructure Guidelines: Ensures compliance with regional standards, focusing on safety, functionality, and sustainability in public infrastructure projects.

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Choosing the right standard depends on your project’s goals:

• If your primary focus is on occupant health and well-being, the WELL Building Standard is the best choice.
• For projects aiming to achieve sustainability and energy efficiency, LEED is the most comprehensive option.
• If you need to ensure HVAC system performance and energy efficiency, adhering to ASHRAE standards is essential.
• For public sector projects in Alberta, which includes schools, following the Alberta Infrastructure Guidelines ensures compliance with local regulations and safety standards.

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Each of these standards--WELL, LEED, ASHRAE, and the Alberta Infrastructure Guidelines—offers unique benefits that can enhance building design, operation, and occupant well-being. By understanding their differences, you can select the most appropriate framework for your project, ensuring that your building meets its specific goals for health, sustainability, and performance.
Whether you’re looking to improve indoor air quality, reduce energy consumption, or create a healthier environment for occupants, these standards provide the tools and guidance needed to achieve success.

In the world of innovation and technology, 3D printing has emerged as a beacon of creativity, offering endless possibilities for makerspaces, schools, libraries, and small businesses. However, as we delve into the realm of creating and materializing our imaginations, it's crucial to address the elephant in the room: the safety concerns associated with 3D printing. Based on recent findings and recommendations from the CDC and NIOSH, this blog post aims to shed light on the potential hazards of 3D printing and guide you through implementing effective safety measures.

A copy of the CDC and NIOSH Publications - Approaches to Safe 3D Printing: A Guide for Makerspace Users, Schools, Libraries, and Small Businesses
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The safety of 3D printing doesn't stop at engineering controls. Ensuring a comprehensive safety strategy involves adopting additional measures such as:

• Exhaust Ducting: For larger printers or those used extensively, connecting to exhaust ducting that leads outdoors can help manage emissions effectively.
• Negative Air Pressure: Maintaining a negative air pressure differential in the printing area prevents the spread of contaminants to adjacent areas.
• Filtered Ventilation: Using HEPA-filtered LEV, especially when dealing with VOCs, adds an extra layer of protection.
• Safe Post-Processing: Employ ventilated enclosures or downdraft tables for tasks involving chemicals or mechanical finishing to capture emissions and particulates.

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UL-200B_1 - Safe Use of 3D Printing for Institutions of Higher Education is a guidance document published on May 8, 2023, by Underwriters Laboratories Inc. It aims to provide a resource for the safe use of 3D printing in higher education institutions. Key sections and topics include:
Overview and Purpose:

• The document emphasizes the importance of managing safety and health considerations associated with 3D printing, which is increasingly prevalent in higher education.
• It focuses on material extrusion and vat photopolymerization printing methods.

Health and Safety Concerns:
The document highlights potential hazards such as exposure to ultrafine particles (UFPs), volatile organic compounds (VOCs), and other emissions from 3D printers.

• It underscores the need for proper ventilation, filtration, and protective equipment to mitigate these risks.

Guidance on Safe Operation:
Detailed recommendations are provided for the safe operation of 3D printers, including pre-printing, during printing, and post-printing processes.

• Guidelines cover the use of personal protective equipment (PPE), proper handling of materials, and maintenance of a clean work environment.

Risk Management:
The document suggests developing a risk management program that includes inventorying 3D printers, assessing hazards, and implementing safety protocols.

• It recommends a hierarchy of controls, such as elimination, substitution, engineering controls, administrative controls, and PPE.

Additional Resources:

• Chemical Insights Research Institute
  
• UL Research Institute
  
• 3dprint.com

Indoor Air Quality (IAQ) is a pivotal aspect of occupational health and safety, particularly in construction trailers. This construction office consisted of 14 relocatable trailers positioned to make 10,000 square foot office space, that house a construction management team of 80-90 staff at any given time.  These office trailers were serviced by 14 independently operated HVAC system that operated in demand mode.  Meaning air was only delivered to the space when there was a demand for either heat or cool air.  The only consistently operating fans were the 2 bathroom exhaust fans of approximately 200 cfm each.  Each perimeter room had windows that would open but the occupants didn’t appreciate all the surfaces being covered with dust.
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​The case of The Stuffy Construction Office is a striking example, where high carbon dioxide (CO2) levels, close to 3,000 parts per million (PPM), signal a significant air quality concern. These levels, while not posing immediate health risks, indicate insufficient ventilation, leading to dissatisfaction and potential health issues. This situation also highlights a lack of compliance with ASHRAE standards, underlining the need for effective air quality improvement strategies in such environments.
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CO2 levels are critical indicators of air quality in workplaces. In Stuffy Construction Office, CO2 concentrations far exceeded the ASHRAE guidelines for air quality, pointing to inadequate ventilation in the construction site. Elevated CO2, along with other indicators of indoor air pollution in workplaces, can reduce cognitive function and overall comfort, making carbon dioxide monitoring an essential aspect of workplace environmental health.
Short-term Solutions: To immediately address the construction trailers air quality, opening windows can offer a quick fix, enhancing natural ventilation and reducing CO2 levels. This step, while simple, is a crucial part of air quality improvement strategies in such confined spaces.
Long-term Solutions: Long-term solutions focus on HVAC system upgrades and ensuring proper ventilation in construction sites. Conducting a comprehensive air quality assessment, particularly by certified industrial hygienists and registered occupational hygienists, can identify necessary upgrades to the HVAC system. These upgrades are vital to ensure compliance with occupational health and safety standards and to maintain optimal IAQ solutions for construction.
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Western Health & Safety, is backed by expertise in occupational hygiene consulting, can offer substantial assistance in tackling IAQ challenges. Our team, equipped with certified industrial hygienists, can provide thorough air quality assessments, develop customized solutions, and ensure WorkSafeBC compliance. Our approach includes HVAC system evaluations, implementation of carbon dioxide monitoring systems, and ongoing support to maintain a healthy indoor environment in construction trailers.
Conclusion The high CO2 levels in The Stuffy Construction Office emphasize the importance of maintaining robust indoor air quality in construction workplaces. Tackling these challenges requires immediate actions, such as improving natural ventilation, and strategic long-term solutions, including HVAC upgrades and regular air quality assessments. Adhering to WorkSafeBC compliance and ASHRAE guidelines ensures not only a safe but also a productive working environment. Western Health & Safety's commitment to providing effective IAQ solutions underscores the essential role of proactive measures in safeguarding employee health and indoor air quality in construction settings.

Recently, the Centers for Disease Control and Prevention (CDC) released new building ventilation guidance that emphasizes the importance of adequate airflow and upgraded air filtration systems in reducing the transmission of airborne pathogens. The guidance highlights the target of achieving at least 5 air changes per hour (ACH) and utilizing enhanced filters to improve indoor air quality. This development has significant implications for building owners, managers, and individuals concerned about their health and well-being. In this blog post, we will explore the key takeaways from the CDC's new guidance and its importance in creating healthier indoor environments.
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The CDC's new building ventilation guidance, which emphasizes achieving 5 ACH and implementing upgraded air filters, is a significant step toward creating healthier indoor environments. By prioritizing ventilation and filtration, building owners and managers can mitigate the spread of airborne pathogens and improve overall indoor air quality. As we continue to navigate the challenges of respiratory infections, adopting these guidelines is crucial in safeguarding the health and well-being of occupants and creating spaces that support optimal performance and comfort.

WHS Industrial Hygienist who service Alberta and BC can help by performing HVAC inspections and perform and conduct indoor air quality investigations.
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