High Rise Residential - smoke detector/CO2 mon. combined device?

Hi Marian,
I think you need to go back to your design engineers and ask them to show you this combo CO2/smoke detector they propose. I have yet to see such a device available. I have a feeling that they are confused between CO and CO2. There are many CO/smoke detectors out there, but CO is not a surrogate for CO2. That said if you measured and alarmed based on CO2 in EVERY space (not just the residential unit as a whole) perhaps you could meet the credit requirement via an alternative compliance path. Your rationale would be that by ensuring CO2 levels are acceptable in EVERY space then the OA ventilation rate must be at least the rate required by 62.1. To reiterate though, first make sure your design engineer is up to speed on their high school chemistry. :-)
Good luck,
John

Hi Marian,
Our company is working on a similar high rise with 280 apartment units, and the usual common areas (leasing, fitness, lounge etc.). We are debating whether or not the apartment units will require the CO sensors, or can we exclude them because they are not "densely occupied"? We would in that case, just install the sensors in the common areas. Would this meet the credit requirements? Can you please provide some guidance based on your experience with this strategy? Thank you!

Thanks for the quick reply Marian. I think I may have misinterpreted this but each space within each apartment may require a CO2 sensor?? That would be absurdly expensive, I completely agree with you.

However, my thinking was that:
1. Apartment units will not require CO2 sensors since they are not densely occupied.
2. Leasing, fitness, lounge, and other common areas would require CO2 sensors.

Marian and VB:
The apartment units should not be considered densely occupied spaces, and therefore, they would not require CO2 sensors regardless as to whether they were provided for the unit as a whole or within each room within the unit. Providing CO2 sensors in the fitness, lounge, and other commons areas would be required, so long as those spaces are considered densely occupied, as well. That is not to say that your outdoor air units would not need outdoor airflow measurement devices. Hope that helps!

Hi VB,
Remember there are two requirements in this credit. If the space is not densely occupied (e.g., the apartment units) then the ventilation system serving those spaces must have direct measurement of the incoming outdoor air at the system level. Not sure how you're getting outdoor air into the units, but you will need to measure it and have an alarm if it varies by more than 10% from setpoint. You may need this for the common areas as well in addition to the CO2 sensors depending how your ventilation systems are designed.
Good luck,
John

Thank you Marian, Lauren, and John. Your comments and experiences have been tremendously helpful in clearing up the questions we had.

Correct