To calculate people outdoor airflow rate in breathing zone code#

To calculate people outdoor airflow rate in breathing zone code#

In section v above, the Texas Administrative Code calls for an exhaust fan, controlled by the instructor, sufficient in size to exhaust the total volume of the room in 15 minutes, or be capable of providing an exhaust rate of 4 ACH.

If electricity, gas and or/water are provided in student areas, emergency shut-off controls shall be provided for each in a location accessible to the instructor but not easily accessible to the students.

A minimum of 6 linear feet of horizontal workspace shall be provided for each student in each middle school and high school science laboratory and science laboratory/classroom.

The exhaust shall be vented to the outside above the roof and away from air vents. The exhaust fan shall be of sufficient size to exhaust the total volume of the room within 15 minutes.

An exhaust fan controlled by the Instructor shall be provided in all rooms where hazardous or vaporous chemicals are to be used or stored.

There is no minimum ventilation rate called out, so we refer back to the minimum ventilation rate given by ANSI/ASHRAE 62.1 – 2010. In chemical storage rooms, the ventilation system shall exhaust the air to the outside, and shall not be recirculated back into the space.

Ventilation system such that air from the science rooms is not recirculated into non-science areas.

Within the body of the Rule, the minimum provisions for a school science laboratory, science classroom, science laboratory/classroom, science preparatory room and chemical storage room shall include the following provisions: The Texas Administrative Code, Title 19, Part 2, Chapter 61, Subchapter CC, Rule 61.1036 is the Commissioner’s Rules Concerning School Facilities. In addition, Table 6-4 specifies a minimum exhaust rate of 1.00 cfm per square foot of Educational Science Laboratories. (Note: for any given science laboratory, and assuming a 9 foot ceiling height, this equates to roughly 2.9 air changes per hour (ACH)). Using the default occupancy of 25 persons per 1000 ft 2, the minimum ventilation for a science laboratory is 0.43 cfm/ ft 2 hzh. Utilizing Table 6-1, under the category Educational Facilities, Science Laboratories have the following information provided: Ra = outdoor airflow per unit area as determined by Table 6-1 Rp = outdoor air rate per person as determined by Table 6-1 Where Vbz = breathing zone outdoor airflow The breathing zone outdoor airflow is defined as the outdoor airflow required in the breathing zone of the occupied space as follows:

It is important to note that ventilation is defined as outdoor air. Most of the modern model codes (Uniform Mechanical Code, International Mechanical Code) refer to ANSI/ASHRAE Standard 62.0-2010 Ventilation for Acceptable Indoor Air Quality as the reference for ventilation rates according to occupancy and type of facility. There are, however, minimum ventilation (outdoor air ) rates and minimum exhaust rates mandated by code.

In point of fact, there is no code-mandated air exchange rate for any laboratory, including K-12 Educational Science Classrooms. A common question is “What is the minimum ventilation rate for an educational science classroom?” This is often followed by “What is the code requirement for minimum ventilation rates in an educational classroom?” When it comes to prescribing the necessary engineering controls and safety features to provide a safe learning environment for our children in the K-12 Educational Science Classroom, we must sift through the over-abundant information available to determine what is, in fact, code and regulatory requirements versus what is anecdotal guidelines. We as design professionals are obligated to provide safe, cost effective, and appropriate engineering solutions to our clients.

January 14th, 2019 by Dan Milgrim, PE, Director of Science & Technology