Most local regulations for indoor air quality are designed around ASHRAE Standard 62. This standard specifies the minimum amount of outdoor air flow into an occupied space to be between 15 to 60 CFM per person, but more commonly building regulations require 15 to 20 CFM per person. Besides actually measuring the air flow, ASHRAE also defines indoor air quality using the concentration of carbon dioxide gas in the air. Carbon dioxide is recommended to be less than 1000 PPM. When sizing the air handling unit for a building, engineers will make the design exceed the maximum occupancy in the building or space to ensure that they will always be able to meet the minimum air requirements. In most cases, buildings or mix used spaces rarely are occupied at these maximum levels, thus the amount of conditioned air supplied is usually much greater than what is required. As building owners aim to reduce energy costs and operate buildings more efficiently, wasted energy of conditioning unneeded outside air has been a good place to start. Continue reading “Energy Savings from On-Demand Ventilation”
As standards become stricter for monitoring indoor air quality (IAQ) it is important to understand that the readings from your instrumentation are correct and accurate. When monitoring carbon dioxide levels for on-demand ventilation, it is imperative that you account for barometric pressure as it can create a false sense of accuracy when controlling an HVAC system. Continue reading “How Barometric Pressure Affects Carbon Dioxide Readings”
Dwyer offers several carbon dioxide measuring products that use non-dispersive infrared sensors as the sensing element. Carbon dioxide sensors are commonly used in building automation systems to monitor air quality. The level of carbon dioxide is indirectly proportional to the amount of people in a space and can be used to adjust ventilation for the space.
There are two basic types of gas sensing technologies: chemical reaction and infrared spectroscopic. Most chemical reaction sensors are electrochemical sensors, which are not as reliable as they can interact with multiple gases and wear from interaction with the gas. Continue reading “Non-Dispersive Infrared, NDIR, Carbon Dioxide Sensors”
Wall mount humidity sensors for building automation system (BAS) applications are produced and sold by several different companies and have a reputation of poor accuracy despite specifications from suppliers. There is a rational reason why these instruments appear to read outside of their stated accuracy, which in turn causes users to be frustrated with the results.