Diagram illustrating the Hierarchy of Controls: Elimination, Substitution, Engineering Controls, Administrative Controls, and Personal Protective Equipment (PPE).

The Hierarchy of Controls: A Systematic Approach to Pathogen Management

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When it comes to protecting people from pathogens and other workplace hazards, not all control measures are created equal. The Hierarchy of Controls is a systematic approach that prioritizes the most effective strategies for preventing exposure to hazards, including infectious agents. 

What is the Hierarchy of Controls? 

The Hierarchy of Controls is a framework used by safety professionals to implement effective control solutions. Developed by the National Institute for Occupational Safety and Health (NIOSH), this approach organizes hazard control strategies from most to least effective: 

  1. Elimination – Physically remove the hazard 
  2. Substitution – Replace the hazard 
  3. Engineering Controls – Isolate people from the hazard 
  4. Administrative Controls – Change the way people work 
  5. Personal Protective Equipment (PPE) – Protect the worker with PPE 

Most Effective: Elimination and Substitution 

At the top of the hierarchy are the most effective control measures: 

  • Elimination involves completely removing the hazard from the workplace. For pathogens, this might mean identifying and removing infected individuals from the environment or eliminating conditions that allow pathogens to survive. 
  • Substitution replaces a hazard with a less dangerous alternative. While challenging to apply directly to pathogens, it might involve replacing high-risk procedures with safer alternatives that achieve the same outcome. 

Engineering Controls 

Engineering controls are physical changes to the workplace that isolate people from hazards. These are particularly valuable for pathogen control and include: 

  • Advanced Disinfection Technologies 
  • Negative pressure rooms for airborne pathogens 
  • High-efficiency air filtration systems 
  • Physical barriers like sneeze guards 
  • Proper ventilation to reduce airborne transmission 

Administrative Controls 

Administrative controls change the way people work to reduce exposure: 

  • Developing policies for sick leave and remote work 
  • Implementing hygiene protocols 
  • Creating cleaning and disinfection schedules 
  • Training employees on infection prevention 
  • Adjusting work schedules to reduce crowding 

Least Effective: Personal Protective Equipment 

At the bottom of the hierarchy is PPE, which includes: 

  • Respirators and face masks 
  • Gloves 
  • Face shields 
  • Gowns and protective clothing 

While essential, PPE is considered the last line of defense because it relies on proper use by individuals and doesn’t eliminate the hazard at its source. 

Why The Hierarchy of Controls Works 

The Hierarchy of Controls provides a structured method for addressing pathogen risks. By focusing on elimination and engineering controls first, organizations can implement more reliable protections before resorting to measures that depend on individual compliance. 

For effective pathogen management, the best approach usually combines multiple controls across different levels of the hierarchy, creating layers of protection against infectious disease transmission. 

To learn more, check out the information at the source – The CDC.

Crowded indoor space with ASHRAE logo, representing efforts toward better indoor air quality.

Breathe Easy: ASHRAE’s Guidelines for Better Indoor Air

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Ever wonder what makes the air inside buildings healthy to breathe? ASHRAE publishes standards and guidelines for indoor air quality. Here’s what you need to know in plain language. 

What Are These Guidelines? 

Think of ASHRAE Standard 62.1-2022 as a rulebook for good indoor air in commercial facilities. It sets minimum requirements for ventilation (bringing fresh air in) and other measures to keep indoor air healthy for people. The goal is simple: make sure the air we breathe indoors won’t make us sick. 

Who Do These Guidelines Affect? 

These guidelines apply to most buildings where people spend time, except for residential homes. They’re used when: 

  • Building new structures 
  • Adding to existing buildings 
  • Making certain changes to buildings 
  • Improving air quality in older buildings 

Better Indoor Air: The Main Points Made Simple

Fresh Air Systems 

The guidelines explain how to design, install, and maintain systems that bring fresh air inside and clean the air that’s already there. 

Indoor Air Pollutants 

The rules address things that can make indoor air unhealthy, including: 

  • Outdoor pollution coming inside 
  • Dust and chemicals from construction 
  • Moisture and mold 
  • Cigarette smoke 

Outdoor Air Quality 

Before designing a ventilation system, builders need to check if the outdoor air in the area is clean enough. If it’s not, they must add filters or air cleaners to remove particles and harmful gases. 

Equipment Requirements 

The guidelines have specific rules for air system parts like: 

  • Where outdoor air enters the building (keeping these intakes away from exhaust fans, garbage areas, and other sources of pollution) 
  • Surfaces that the air flows over (making sure they resist mold) 
  • Drain pans (ensuring they don’t become breeding grounds for bacteria) 
  • Humidifiers (devices that add moisture to the air) 

There’s also emphasis on preventing Legionnaires’ disease, a serious type of pneumonia that can spread through water systems. 

Air Classification 

Not all indoor air is equal. The guidelines sort air into four classes based on how contaminated it might be and set rules for when this air can be reused or moved to other areas. 

Determining How Much Fresh Air Is Needed 

Designers can use several methods to figure this out: 

  • A straightforward approach based on room type and size 
  • A more complex method analyzing specific pollutants 
  • Guidelines for systems using natural airflow (like windows) 

Keeping It Clean 

The rules emphasize keeping air ducts clean during construction and making sure fresh air dampers (valves that control airflow) work properly before people move in. 

Ongoing Maintenance 

Regular upkeep of ventilation systems is required to ensure they continue working effectively. 

Checking Results 

For projects using the more complex design method, testing is required after completion to verify the air is actually clean. 

ASHRAE: Your Resource for Better Indoor Air 

These guidelines are constantly being updated as new research emerges. While following them isn’t legally required (unless local building codes say so), they’re widely recognized as the gold standard for healthy indoor air. By understanding these basics, you can better appreciate the behind-the-scenes work that goes into making the air in your workplace, school, or public buildings safe to breathe. To fully understand the standard, you can access a readable version of the entire document by visiting ASHRAE’s Technical Resources. 

 

A person holding a smartphone displaying their IAQ monitoring system, connected to a smart thermostat for real-time indoor air quality control.

The Evolution of IAQ Monitoring: Past, Present, and Future

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The Early Days: Temperature-Only Monitoring 

If you go back in time, the original indoor air quality (IAQ) sensors only measured temperature and were usually tied into the thermostat to control the HVAC system. These basic IAQ monitoring sensors/thermostats served a single purpose: maintaining comfortable temperatures in indoor spaces. They operated on simple principles detecting when temperatures deviated from set points and triggering heating or cooling responses accordingly. 

The Smart Revolution 

Those basic sensor/thermostats have evolved dramatically into smart devices that now include other measurements like humidity and allow remote control of HVAC operation from users’ phones. This transformation has been driven by several factors: 

  • Advancements in sensor technology making multi-parameter monitoring affordable 
  • The rise of IoT (Internet of Things) connectivity enabling remote access 
  • Increased awareness of how humidity affects both comfort and health 
  • Consumer demand for more convenient control options 

Today’s smart thermostats don’t just react to temperature changes—they learn occupancy patterns, adjust to user preferences, and even integrate with other smart home systems. 

The Integration Era: Connecting to Building Management Systems 

Simultaneously, stand-alone sensors have evolved to include humidity monitoring and are often tied to building management systems (BMS) to control the operation of the HVAC system, adjusting both temperature and humidity. This integration allows for: 

  • Centralized monitoring of multiple parameters across entire buildings 
  • Automated responses to changing conditions 
  • Data collection for trend analysis and system optimization 
  • Improved energy efficiency through precise environmental control 

More advanced sensors are incorporated in demand ventilation control systems that manage the amount of outside air being brought in based on the amount of carbon dioxide measured in a space. This approach recognizes that CO₂ levels serve as a proxy for occupancy and potential air staleness. 

Today’s Comprehensive IAQ Monitoring 

The current generation of IAQ sensors offers unprecedented visibility into indoor environments. Modern systems can monitor: 

  • Temperature: Still fundamental for comfort and energy efficiency 
  • Humidity: Critical for preventing mold growth and maintaining comfort 
  • Carbon Dioxide (CO₂): Indicator of ventilation adequacy and occupancy 
  • Particulate Matter (PM2.5, PM10): Tiny particles that can cause respiratory issues 
  • Volatile Organic Compounds (VOCs): Gases emitted from products and materials that can cause health problems 
  • Nitrogen Dioxide (NO₂): Often from combustion sources like gas stoves 
  • Ozone (O₃): Can enter from outdoors or be generated by some office equipment 

When these comprehensive sensors are integrated with the BMS, the system can make real-time adjustments to airflow, temperature, filtration, and even the percentage of outside air to maintain optimal indoor air quality. 

The Missing Piece: Pathogen Monitoring 

So, if I can put a sensor in my facility that measures temperature, humidity, carbon dioxide, particulate matter, volatile organic compounds (VOCs), and then tie that to the BMS to make adjustments to air flow, temperature, and even percentage of outside air, what else would I need? 

The major piece of IAQ that has been overlooked for many years prior to the release of ASHRAE 241-2023 is the effect of pathogens. We don’t want VOCs in our air because they make us sick. Similarly, we should be concerned about the amount of airborne pathogens like different variants of the flu virus or even COVID-19. 

Unfortunately, there are currently no commercially viable sensors that can be utilized to monitor specific pathogens in the air in real-time. Many sensors provide indexes that are derived from other measurable factors to show the likelihood of people getting sick from each other, but nothing measures the actual pathogen concentration directly. These proxy measurements include: 

  • Particulate matter in respirable size ranges: May contain pathogens 
  • CO₂ as an indicator of exhaled breath: Higher levels suggest more potential for person-to-person transmission 
  • Relative humidity: Some pathogens survive better in very low or very high humidity 

The Path Forward: Integrated IAQ Monitoring Approaches 

This gap in direct pathogen detection highlights why it is important for facilities to: 

  1. Design to baseline conditions: Maintain environments that are designed to handle the normal pathogen level they expect 
  2. Implement adaptive strategies: Have measures in place to deal with spikes in pathogen levels, such as during flu season 
  3. Layer protective measures: Combine ventilation, filtration, temperature and humidity control, and when necessary, active disinfection devices 
  4. Monitor surrogate parameters: Track the indicators we can measure to estimate pathogen risk 
  5. Stay informed: Keep up with emerging technologies that may eventually allow direct pathogen monitoring 

Emerging IAQ Monitoring Technologies 

Research laboratories and technology companies are working on several promising approaches to real-time pathogen detection: 

  • PCR-on-a-chip technologies: Miniaturizing the same technology used in COVID testing 
  • Spectroscopic methods: Identifying pathogens based on their light absorption profiles 
  • Biosensors: Using biological elements to recognize specific pathogens 
  • AI-powered multi-parameter analysis: Using machine learning to identify patterns in multiple IAQ parameters that correlate with pathogen presence 

The Future of Intelligent IAQ Monitoring

As IAQ sensing technology continues to evolve, we’re moving closer to comprehensive monitoring systems that can help maintain truly healthy indoor environments. While direct pathogen detection remains elusive in commercial applications, the integration of multiple IAQ parameters with intelligent building management systems represents a significant step forward in protecting occupant health and well-being. 

The future of IAQ monitoring will likely combine advanced sensing technologies with predictive analytics to not just react to poor air quality, but to anticipate and prevent it—ultimately creating spaces that actively promote health rather than merely avoiding harm. 

AHR 2025 logo sign at the entrance of the Orlando conference, welcoming attendees from the HVAC industry.

CASPR Technologies at AHR 2025: Elevating Indoor Air Quality in the HVAC Industry

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AHR 2025 logo sign at the entrance of the Orlando conference, welcoming attendees from the HVAC industry.
ASHRAE logo displayed at AHR 2025 conference, highlighting the organization’s leadership in HVAC and indoor air quality standards.

The AHR 2025 conference in Orlando was an unparalleled experience for CASPR Technologies, bringing together industry leaders, innovators, and professionals from across the HVAC sector. The event served as the perfect platform for us to connect with experts, exchange ideas, and demonstrate how CASPR’s advanced technology is setting new standards for Indoor Air Quality (IAQ). Conversations throughout the event reaffirmed what we already knew—IAQ is no longer an afterthought. It has become a fundamental pillar of HVAC system design, implementation, and maintenance. As regulatory standards continue to evolve and awareness grows, HVAC professionals are seeking proven, data-driven solutions that ensure both safety and efficiency in every environment. Our team at CASPR Technologies was proud to be at the forefront of these discussions, driving innovation and education within the industry.  


The HVAC Industry is Bigger Than Ever 

AHR 2025 was a testament to the rapid growth and innovation happening within the HVAC industry. Walking the show floor, we were immersed in an environment that showcased the scale, diversity, and impact of the industry’s evolution. With thousands of exhibitors and attendees, it was clear that HVAC is a driving force behind healthier, more efficient indoor environments. The range of technologies on display—from cutting-edge filtration systems to AI-driven building automation—reinforced how IAQ is now woven into the very fabric of HVAC innovation. Whether in large-scale commercial applications, residential solutions, or specialized healthcare settings, there is an increasing demand for smarter, more effective air quality solutions. CASPR Technologies’ role in this landscape was undeniable, as we demonstrated how our continuous disinfection technology is revolutionizing the way air and surfaces are treated for safety and cleanliness. 


Indoor Air Quality Takes Center Stage 

One of the most notable shifts at AHR 2025 was the undeniable mainstream focus on IAQ. In past years, IAQ was often viewed as an added benefit—something to consider after primary HVAC functionalities were addressed. This year, however, it was front and center in every conversation. Whether discussing air purification, improved filtration, or next-generation pathogen treatment, professionals across the board recognized that effective IAQ solutions are essential for occupant health and safety. 

Moreover, we had the opportunity to engage with engineers, facility managers, and industry decision-makers who were all eager to learn how they could integrate validated, long-term IAQ solutions into their existing systems. Our team emphasized the importance of maintaining both air and surface cleanliness, as pathogen mitigation strategies must go beyond traditional approaches to create truly safe indoor environments. As regulatory bodies continue to set stricter standards for indoor air quality, it’s clear that data-backed, continuously active solutions like CASPR’s are becoming a necessity rather than an option. 

CASPR Technologies at AHR 2025 Takeaways: The Growing Importance of Pathogen Treatment 

At AHR 2025, pathogen treatment emerged as one of the most pressing topics in IAQ discussions, highlighting a growing industry-wide realization: true disinfection goes beyond air filtration—it must also address surface contamination. While traditional HVAC solutions have focused primarily on airborne pollutants, there is now an increasing demand for comprehensive, real-time mitigation strategies that tackle both airborne and surface-borne pathogens. 

As awareness grows around the role of pathogens in indoor environments, industry professionals are actively seeking proven solutions that don’t just capture contaminants but actively neutralize them. CASPR Technologies’ continuous disinfection technology captured the attention of engineers, facility managers, and HVAC specialists alike, who recognize that passive filtration alone is no longer enough. The ability to provide ongoing, automated pathogen reduction—without the use of chemicals or manual intervention—is becoming a critical requirement for modern IAQ strategies. 

Pathogen mitigation is no longer a reactive measure—it’s a proactive necessity. Schools, hospitals, commercial buildings, and residential spaces alike are prioritizing IAQ solutions that offer real-time, continuous protection against bacteria, viruses, and mold. Professionals expressed a strong desire for technologies that are not only validated by scientific data but also seamlessly integrate into existing HVAC systems without requiring costly modifications or downtime. 

The consensus was clear: effective, real-time pathogen mitigation is no longer just a competitive advantage—it’s an essential component of any serious IAQ strategy. As regulations tighten and industry standards evolve, there is a heightened expectation for continuous, scientifically backed solutions that can proactively reduce pathogens in the air and on surfaces. 

ASHRAE 241 and the Need for More Data 

A crucial industry discussion at AHR 2025 centered around ASHRAE 241, a new standard designed to provide guidelines for pathogen mitigation in indoor environments. While there is a growing push for IAQ advancements, one major challenge remains—the lack of published data for many existing technologies. Industry leaders stressed the importance of transparency in testing, safety validation, and efficacy reporting to ensure that businesses and consumers can make informed decisions about the technologies they implement. 

“I was surprised to find out how little people knew about IAQ standards and how a lot of the industry has no testing,” stated CASPR Representative Roberto Bonilla. 

CASPR Technologies has long been committed to setting the benchmark for industry standards. As part of our mission to deliver scientifically validated solutions, CASPR was the first technology to be tested for both safety and efficiency under ASHRAE 241 standards. This commitment to data-driven innovation positions CASPR Technologies as a trusted leader in the IAQ space, providing stakeholders with real, measurable results that demonstrate the true impact of our technology. 

CASPR Technologies at AHR 2025: A Packed Room and Engaging Conversations 

One of the highlights for CASPR Technologies at AHR 2025 was the overwhelming turnout for our paper presentation, ‘Assessing Indoor Air Quality in a Comparative Study Among ASHRAE Ventilation Standards Compared to a Control with a Continuous Active In-Room Air Cleaning Device.’  With over 120 industry professionals in attendance, the room was filled with engineers, facility managers, and HVAC experts eager to dive deeper into IAQ advancements. 

The level of engagement and thoughtful questions from attendees reinforced that IAQ is no longer an afterthought—it’s a critical priority for the industry. Throughout the presentation, we discussed the importance of data-driven decision-making in IAQ solutions and how continuous active air cleaning devices can complement ASHRAE ventilation standards. The discussions that followed were not only insightful but also highlighted the growing demand for validated, real-world data on the effectiveness of air purification technologies. 

Many professionals expressed keen interest in how CASPR’s continuous disinfection solutions could be integrated into their existing HVAC systems to enhance air quality and pathogen mitigation. The enthusiasm and dialogue that emerged from this session demonstrated the need for transparent testing, standardized guidelines, and proven results in IAQ technology—something CASPR is committed to delivering. 

AHR 2025 provided the perfect platform to engage with industry leaders and share groundbreaking research, and we’re excited to continue these conversations as we push the boundaries of IAQ innovation. 

Innovation at Every Level 

Innovation in HVAC isn’t just about upgrading large-scale systems—it’s about refining and enhancing every individual component to create a more efficient and effective IAQ strategy. From advanced sensors that monitor air quality in real time to next-generation filtration technologies that capture even the smallest particulates, the industry is experiencing a wave of breakthroughs designed to optimize air circulation, purification, and disinfection. Engineers and manufacturers are focusing on smarter, more adaptable solutions that integrate seamlessly into both new and existing HVAC infrastructures, making high-quality indoor air more accessible than ever before. These advancements are not just about compliance with evolving standards—they are about fundamentally reshaping how we think about air quality in homes, offices, hospitals, and public spaces. 

At CASPR Technologies, we are thrilled to be part of this movement, pioneering continuous disinfection technology that works in tandem with HVAC systems to ensure that indoor environments remain as safe and healthy as possible. Unlike traditional air treatment methods that rely on passive filtration alone, our technology actively neutralizes pathogens in the air and on surfaces, providing a comprehensive approach to IAQ improvement. Whether it’s for schools, healthcare facilities, commercial spaces, or residential buildings, our goal is to make clean, purified air the standard, not the exception. By pushing the boundaries of what’s possible in HVAC and IAQ innovation, CASPR Technologies is committed to shaping the future of indoor air quality—one breakthrough at a time. 

 

CASPR Technologies AHR 2025: A Successful Event with a Bright Future 

Reflecting on our experience at AHR 2025, one thing is clear—the future of IAQ has never been stronger. The sheer level of interest, engagement, and collaboration we witnessed at the event speaks to the growing demand for innovative air quality solutions. The industry is evolving rapidly, and businesses are prioritizing health-focused, sustainable technologies more than ever before. 

For CASPR Technologies, this event was more than just an opportunity to showcase our technology—it was a chance to be part of an industry-wide movement towards better, safer indoor environments. The connections we made, the conversations we had, and the enthusiasm we witnessed all point to an exciting future for IAQ innovation. 

To everyone who stopped by our booth, attended our presentation, and engaged with us in meaningful discussions—thank you. Your passion and curiosity inspire us to continue pushing the boundaries of what’s possible in IAQ and HVAC technology. We look forward to the future, knowing that together, we can redefine indoor air quality and make every indoor space a safer place to live and work. 

 

Modern convention center with spacious exhibition halls, designed to support healthy indoor air quality through advanced ventilation and air monitoring systems.

Designing for Indoor Air Quality: VOCs, Particulate Matter, and Pathogens

by Insights

The Indoor Air Quality Challenges of Exhibition Spaces 

During a recent visit to a large convention center, I spoke with the engineering team about their indoor air quality challenges. One engineer highlighted a unique issue: installing thousands of yards of new carpet for exhibitions leads to significant VOC surges. We explored solutions ranging from temporary space purges with outside air to systematic design approaches for continuous VOC reduction. 

Automated Responses to Environmental Contaminants 

This scenario illustrates a broader application for commercial spaces. Modern buildings can integrate VOC sensors with Building Automation Systems (BAS) to trigger automated responses to environmental changes. These sensors are readily available and easily incorporated into BAS to manage contamination events effectively. 

ASHRAE Guideline 44 addresses this concept in relation to outdoor contaminants like wildfire smoke—where the appropriate response is often to reduce rather than increase outside air intake. Similarly, particulate matter from wildfires can be monitored with sensors that adjust ventilation and recirculation rates accordingly. 

Design Standards for Normal Conditions 

Buildings can be designed with static environmental standards to address “normal” VOC and particulate levels. The ASHRAE 62.1 Indoor Air Quality Procedure (IAQP), compared to the Ventilation Rate Procedure (VRP), offers a more precise and often more energy-efficient approach to maintaining acceptable indoor air quality under standard conditions—assuming no unexpected external contaminants. 

The Pathogen Challenge 

But what happens when the contaminant is anticipated but not easily detectable? Pathogens like H1N1 influenza present a different challenge than VOCs and particulates because they cannot be detected by conventional sensors, making automated BAS responses impossible. 

Designers must therefore implement either: 

  • A strategy that building owners can manually activate in response to increased pathogen concerns 
  • Systems that continuously provide enhanced protection against pathogen transmission between occupants. 

Forward-Looking Indoor Air Quality Solutions 

ASHRAE Standard 241, which we’ve explored in previous discussions, provides guidance for emergency responses to airborne contagions. This standard serves as a valuable resource for designers aiming to create safer, more resilient buildings. 

By considering both everyday air quality concerns and pathogen transmission risks, we can design spaces that protect occupant health under various conditions while maintaining energy efficiency. Want to learn more? Reach out below to get more information from the CASPR team.