Carbon Dioxide Monitoring

January 8, 2003

by David B. South

David B. South,
President of the Monolithic Dome Institute

Carbon Dioxide (CO₂) monitoring is not a new concept, but it's proving to be a tough one to handle. It has to do with the amount of fresh air in a structure.

Most of us have heard of sick buildings. When the air in a building gets polluted with vapors that can be or are harmful to us, the result is a sick building.

Unfortunately, thousands of air borne vapors or particles fall into the polluting category. To complicate matters, we currently have no instrument that can measure all of these possibilities -- at least not at a price most people can afford.

But we do have an affordable way of measuring the concentration of carbon dioxide in a structure. That's important because by looking at the concentration of CO₂, we can estimate the concentration of many other vapors.

Here's the theory: If we can keep CO₂ levels within safe tolerances, we can prevent our homes and offices from getting "sick."

Maintaining reasonable CO₂ levels by measuring and controlling is far better than guessing -- as is most often done in commercial and residential buildings. This ineffective procedure is partly due to the cost of CO₂ meters.

Recently, Monolithic purchased several CO₂ meters. We asked employees to take meters home and begin monitoring. We got some surprising results. Most of the employee homes -- both conventional and Monolithic Domes -- had CO₂ levels above 1200 parts per million, which is too high. Some homes had levels above 4000 PPM.

Why so high? The answer is simple: We don't always get enough fresh air exchange in our homes.

Fresh air is depleted as a result of everyday life in our homes. Besides the occupant's respiratory usage, some household appliances, such as the clothes dryer, help to use up the fresh air supply.

Here's another surprising example: A staff member with many plants in her home got an amazingly high, nighttime CO₂ reading. That happened because plants give off oxygen only when they are in light. At night, they burn oxygen and give off CO₂ -- just as we do.

Of course, the fresh air supply can always be increased by using an exhaust fan or simply opening windows or doors. But we're not always willing to do that. If it's hot outside, we don't want to lose our conditioned air. If it's cold, we don't want to lose our warm air.

So what is the answer?

We are attacking this problem. We're going to continue to monitor our homes as we try out new solutions.

We are currently researching Heat Recovery Ventilators (HRV). At this point, we don't know which system is best. We have tried a few and investigated others. We have even built a fresh air exhange device ourselves and have installed it in my home. Apparently, it's doing the job well, but it's a crude looking device-- not ready to go to market, yet.

The biggest problem we have with most HRVs is price. But there's also a problem with installation and sizing. (Some of our Canadian builders tell us that HRVs are mandatory now in Canada.) We will continue researching HRVs and keep you informed of our findings.

Despite the problems, we think that getting a CO₂ meter is a good idea. Currently, it's the most efficient and affordable way of monitoring CO₂ levels and controlling pollutants. You simply place the meter in a handy spot and check it periodically. When CO₂ reaches an uncomfortable level, you open windows, open doors or turn on fans -- and breathe healthy!

The CO₂ monitor we're using for these tests is available online from us. It is the best we could find at an affordable price.

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