According to ASHRAE standards, the recommended fresh air or outdoor ventilation rates are expressed by cubic feet of air per minute per person, or cfm/person. As a general rule, any occupied building should have a fresh air ventilation rate from five to 10 cfm/person.
The ventilation rate
' A value of 10 litres per second per person is recommended in some building guides as a suitable value for most commercial buildings. In some workplaces, like draughty workshops, it is obvious there is enough air.
Provision of 1 square foot of NFVA for each 300 square feet of attic floor if both following conditions are applicable: At least 40%, but not more than 50% of NFVA is provided by vents located not more than 3 feet below roof's highest point.
What is necessary for adequate general ventilation will depend on factors, such as the amount of floor space per occupant and the work activity. The HSE says the fresh-air supply rate should not normally fall below 5 to 8 litres per second, per occupant.
According to ASHRAE standard 62.1 (“Ventilation and Acceptable Indoor Air Quality in Residential Buildings”), homes need to have at least 0.35 air changes of outdoor air for indoor air per hour to maintain the quality of the indoor air.
ASHRAE (formerly called the American Society of Heating, Refrigerating and Air-Conditioning Engineers) recommends (in its Standard 62.2-2016, "Ventilation and Acceptable Indoor Air Quality in Residential Buildings") that homes receive 0.35 air changes per hour but not less than 15 cubic feet of air per minute (cfm) per ...
The most widely used value is 1 atmosphere (101.3 kPa) or 14.696 psia at sea level and 59 0F (150C). Normal flow rate is 1 atmosphere (101.3 kPa) or 14.696 psia at 32 0F (0 0C).
As a general rule, any occupied building should have a fresh air ventilation rate from five to 10 cfm/person. Keep in mind that these rates may vary by building size. Ventilation rate standards may also differ depending on how spaces within a building are used.
For continuous indoor air quality ventilation, a heat or energy recovery ventilator (HRV or ERV) should provide 0.35 air changes per hour. This calculation must consider the complete occupied volume of the house. This rate can be more easily calculated by allowing 5 CFM per 100 square feet of floor area.
ASHRAE Standard 62.1 & 62.2
“Specify minimum ventilation rates and indoor air quality that will be acceptable to human occupants and are intended to minimize the potential for adverse health effects” is the standard's primary objective.
The ventilation rate indicates how often the room is supplied with fresh air per hour. For this, you need to know the volume of the room (height x width x length = volume in m3 or ft3). The ventilation per hour is then calculated as follows: Volume x ventilation rate = m3/hour or cfm.
A fresh air intake allows the HVAC system to pull fresh air from outside and channel it to rooms via specialized vents. Every home is legally required to have a fresh air intake if a gas appliance, such as a furnace, is installed.
Your air intake is designed to run constantly, brining in a steady flow or fresh air. Some models are equipped with temperature and humidity controls that will turn the unit off if the air coming into the home is too cold, too warm or too humid.
To avoid this, fresh air is supplied as per the number of occupants and the area of the space. The average fresh air requirement per person per second is 8 litres. This is how much air we breathe.
The room's square footage will tell you what the CFM should be (12 x 12 = 144).
15 cfm per person, multiplied by the expected number of occupants.
The average American household needs 100 to 120 gallons per person per day, and a flow rate of about 6 to 12 gallons per minute.
The volume of air that needs to circulate through the system depends on the size of the AC or other HVAC unit. To work effectively, a system needs to circulate 400 cubic feet of air per minute (CFM) for every 1 AC ton.
Best performance for most vehicles is in the 12.5 to 13 AFR range. Going too rich will have the opposite affect and decrease your performance.
Generally, they require ventilation rates of about 5 to 10 L/s of outdoor air for each house occupant or roughly a complete house air change every three hours, but these rates vary according to the number of occupants, house volume, occupant activities, and the presence of indoor sources of pollutants.
ASHRAE 62.2-2016 guidelines call for 1 air exchange every 3-4 hours, so the airflow will need to be measured at the outdoor air inlet with it open.
What is a good CFM for a fan? This entirely depends on the application. For a residential fan you might have in your living room, a CFM of 5,000-6,000 might be totally sufficient. For large warehouses, you might want a fleet of large-diameter HVLS fans that each have a CFM of over 300,000.
If your flow rate is less than 10 litres per minute, you may have what is considered low water pressure. Anywhere between 10 and 15 litres per minute is acceptable but can be improved. A flow above 15 litres per minute is considered good.
With the engine at idle, the MAF's PID value should read anywhere from 2 to 7 grams/second (g/s) at idle and rise to between 15 to 25 g/s at 2500 rpm, depending on engine size. Most manufacturers provide specifications for air flow at idle; some will provide specifications at several engine speeds.