This article is aimed to introduce and explain the metrics collected by the MT14 Air Quality Sensor and how the qualitative ratings are derived and displayed on the Dashboard.
Indoor Air Quality Rating
The Indoor Air Quality (IAQ) Rating is a unique qualitative aggregate rating that can be used as a general indicator for overall air quality. IAQ has five qualitative ratings ranging from excellent, good, fair, poor, and inadequate. It incorporates temperature, humidity, TVOC's, and PM2.5.
Each metric has a weight assigned to it based on the current reading and an aggregated score is calculated. Below is the range how the qualitative rating is assigned to the aggregated score:
Excellent: 93 to 100
Good: 80 to 92
Fair: 60 to 79
Poor: 40 to 59
Inadequate: 20 to 39
Refer to the sections below to see how each metric’s qualitative ratings are attributed to the IAQ calculation.
IAQ score calculation doesn’t include Ambient Noise measurement.
Temperature affects people's comfort, productivity, and willingness to remain inside of a space. The Occupational Safety and Health Administration (OSHA) within the U.S. Department of Labor recommends 68-76°F (20-24.4°C) as the ideal range in the workplace. High temperatures can lead to heat stress and dehydration. Low temperatures can lead to dry air, impairment of the immune system, and general discomfort. 
Humidity levels affect people's comfort, productivity, and respiratory health. High humidity can lead to dehydration (due to excessive sweating), heat rashes, and allergy-like symptoms. High humidity can also promote the growth of harmful mold, viruses, and bacteria. Low humidity can lead to dry skin, sinus irritation, and increased vulnerability to infection. 
Total Volatile Organic Compounds (TVOC) measures the total amount of VOC's in the area. VOC's include a variety of chemicals, such as paints, aerosol sprays, cleaning solutions, pesticides, and automotive products. They can also include chemicals from smoking electronic cigarettes, also known as vaping. High TVOC levels can negatively affect comfort, health, and productivity. Symptoms associated with high TVOC's include sinus irritation, headaches, nausea, and damage to the liver, kidneys, and nervous system. Some VOC's are also known to cause cancer in humans. 
The readings obtained by the sensor gives a Total amount of chemicals in the environment. It doesn’t provide individual concentrations of which chemicals are present in the sampling.
TVOC Refinement Period
On first boot, the TVOC sensor undergoes a refinement period of about 48 hours, where it calibrates the current environment as baseline. MT14's TVOC accuracy varies according to environmental conditions; MT14 readings become more accurate over time if TVOC levels are kept low for the majority of the time.
PM2.5 is particulate matter that is smaller than 2.5 micrometers. These particles are concerning because they are small enough to permeate the mucous membranes in your lungs and can even get into your bloodstream. PM2.5 comes from many sources including automobiles, construction sites, industrial facilities, fires, smokestacks, and cooking fumes along with vaping fumes from e-cigarettes. Prolonged exposure to PM2.5 can lead to respiratory irritation, decreased lung function, heart disease, cancer, and even premature death. 
NOTE: External power is required to collect PM2.5 data from MT14
Ambient Noise (dBA)
Ambient noise levels affect people's comfort, productivity, and hearing health. High ambient noise can make it difficult to concentrate or communicate with others. If ambient noise exceeds 85 decibels for extended periods of time, it can lead to hearing damage and long-term hearing loss.