There’s been a lot of discussion around ASHRAE 62.1, 241 and what it means for building design. 

But for many teams, the bigger question is: 

What’s the difference—and what does it mean for how clean air is delivered in a space? 

We broke it down in a recent white paper. Here are seven takeaways worth understanding before your next project. 

1. Focus Shifts from Ventilation to Clean Air Delivery 

ASHRAE 62.1 is built around ventilation strategies that prioritize outdoor air to maintain acceptable indoor air quality. 

ASHRAE 241 introduces a different metric: Equivalent Clean Airflow (ECAi)—which accounts for all sources of clean air and ties performance more directly to the occupant. 

This shifts how performance is evaluated, from system-level airflow to occupant-level outcomes. 

2. Clean Air Requirements Increase During Elevated Risk Conditions 

ASHRAE 241 is activated during periods of elevated risk through Infection Risk Management Mode (IRMM). 

During these conditions, required clean airflow increases significantly—often several times higher than baseline ventilation targets. 

This is where many existing systems begin to fall short. 

3. Most 62.1-Compliant Systems Will Require Additional Strategies 

Even when a system is fully compliant with 62.1, it may not meet 241 targets during IRMM. 

This gap becomes clearer when you look at real-world scenarios. 

In a typical classroom scenario: (900 square feet, 20 students) 

• 62.1 Requirement:  ~308 CFM from baseline ventilation 

• 241 Target (During IRMM) ~800 CFM required under 241 

• ~492 CFM gap 

Closing that gap is where design decisions start to shift. 

4. Increasing Outdoor Air Isn’t Always the Most Practical Solution 

One approach is to increase outdoor air through the HVAC system. 

But doing so can introduce tradeoffs—higher energy demand, system limitations, and longer implementation timelines. In existing buildings especially, those constraints can limit what’s feasible. 

This is why many teams look beyond ventilation alone. 

5. ASHRAE 241 Allows Multiple Paths to Compliance 

The standard does not prescribe a single solution. 

Clean air can be delivered through a combination of: 

• Outdoor air ventilation 

• Filtered recirculated air 

• Air-cleaning devices 

As long as the required ECAi is achieved, different strategies can be used to meet the target. 

6. In-Room Air Cleaning Can Help Close the Gap 

Because in-room air cleaning devices contribute directly to Equivalent Clean Airflow through validated CADR values, it can be used to help address gaps identified in 241 calculations. 

Solutions like Fellowes Array are designed to support this approach—adding localized, measurable clean air while working alongside existing HVAC systems, rather than requiring them to carry the full load. 

7. Measurement and Verification Are Part of the Standard 

ASHRAE 241 places greater emphasis on calculation, verification, and operational practices to ensure performance is achieved and maintained over time. 

Tools like the Equivalent Clean Airflow Calculator (ECAC) help teams: 

• Define targets 

• Quantify system contributions 

• Confirm whether requirements are met 

This brings more transparency into how air quality is designed and validated. 

Get the Full Breakdown 

These are the high-level takeaways—but the details are where design decisions come together. 

The full white paper walks through: 

• Side-by-side comparisons of ASHRAE 62.1 and 241 

• ECAi calculations and methodologies 

• Implementation scenarios across different building types 

• How systems like Fellowes Array contribute to compliance 

Download the full white paper: