Industry Terms

Air Changes Per Hour (ACH)

Air Changes per Hour (ACH) is a measure of how many times the air within a defined space is replaced with outside air or cleaned air each hour. The higher the ACH the better ventilation and the safer the indoor air quality is.In construction zones the accepted standard 6 ACH. In a hospital’s operating room, the acceptable standard is 12-15 ACH.



Aerosols are produced when particles are suspended in air or gas. For example, aerosol occurs when humans expel fine microscopic droplets through speaking, breathing, or coughing. Often, the aerosol is invisible to the naked eye and can remain suspended in the air for long periods. This is especially problematic for infected aerosols. Since it remains suspended in the air, long after an infected person has left the room, suspended micro-particles can be inhaled into someone else’s respiratory tracts. Infected aerosols fuel airborne transmission, which is why improved ventilation and filtration are crucial for containing airborne diseases.

Airborne Infection Spread

Free-floating infectious particles often attach to dust or water molecules. Humans produce this aerosolized, contagious combination. Once particles are created, they remain suspended in the air. Due to airflow patterns and ventilation issues, these particles can travel for long distances. That is why the recommended lengths of six feet to promote disease containment, especially in indoor environments, aren’t foolproof. Even after an infected person leaves the room, they have already emitted infectious airborne particles that remain suspended. The next person in the room could inhale these particles and continue the chain of infection . Removing particles from the air before inhalation occurs, via rigorous filtration and ventilation protocols, is paramount.


This acronym stands for cubic feet per minute, which is a method of airflow velocity measurement. CFM is calculated by measuring the volume of air that can fit into one room. Measure height, length, and width–then multiply these numbers together. The result is the room’s volume. For instance, a box-shaped room with 100 feet x 50 feet x 20 feet will be 100,000 cubic feet. Angled ceiling and odd additions will complicate this math, but it can still be done. To find the CFM rate, take the total air volume, and divide it by the exchange rate. The exchange rate is how many times per hour you change the air, and this number should be dictated by industry risk level.


This acronym stands for high-efficiency particulate air. Used to reference a specific type of pleated fiberglass filter, HEPA defines air filtration’s highest standards. The minimum requirement is that filters must remove 99.97% of particles that measure 0.3 microns or larger. For perspective, a particle that measures 0.3 microns is 300 times smaller than a human hair. To achieve this efficacy, HEPA filters are designed, certified, and anufactured per the industry’s strictest protocol.

Line of sight efficacy

Ultraviolet germicidal irradiation is one of the most effective methods of sanitation. However, the application must be highly specific to avoid the danger of ineffective methods. Exposed ultraviolet light is dangerous to humans; since it can cause blindness, sunburn, and more. That’s why exposing light to viruses is harmful. It requires emptying a room before conducting sanitation procedures, which eliminates the opportunity for continuous sanitation. Once the room is emptied and the UVC light is activated, disinfection can begin. But UVC light can only eradicate germs, pathogens, and viruses that it can ‘see’. Awkward corners, undersides of tables and desks, and other nooks will be ignored. UVC light, when applied in this manner, is only as useful as what it can see. That’s why Omni Clean Air’s method of bringing the virus to contained UVC bulbs, through workhorse filtration, is the only way to ensure continuous sanitation. This process doesn’t endanger anyone in the room and doesn’t rely on line of sight efficacy.

Medical-grade air purification

There are different standards for air changes per hour in each industry. For instance, in the construction industry with toxic material like asbestos, the average is six air changes per hour. To calculate how many air changes per hour will occur, you’ll need to divide the room’s total volume by the CFM. In operating rooms, the standard is fifteen air changes per hour. Since Omni CleanAir’s machines are being used in nuclear cleanup zones and pandemic response, our machines achieve fifteen air changes per hour. This guarantees the safest air possible.


MERV is a filter standard that stands for minimum efficiency reporting values. This translates to the acronym MERV, which helps establish a filter’s ability to capture particles between 3 and 10 microns. The MERV rating spans the numbers 1 to 16. This rating indicates what percentage of particles–and what size–they can capture. For instance, a MERV rating of 12 means the filter can capture 80% of particles between 1 and 3 microns. A MERV-12 filter can capture 90% or more of particles between 3 and 10 microns.


In the metric system, microns are a unit of length that equals one-millionth of a meter. If an object measures 1 micron, it is invisible to the human eye. For perspective, HEPA filters remove particles that are 0.3 microns or larger. Microns are used to measure cells in biology and particles in the air filtration industry. To emphasize these particles’ size, a human hair is fifty microns wide and is barely visible to the human eye.

Microscopic respiratory droplets

Microscopic droplets are expelled whenever humans breathe, speak, cough, sing, or sneeze. These droplets come from the respiratory system. They can often latch onto other moisture or dust molecules and remain suspended for some time. Depending on the air ventilation flow, these particles can travel an impressive distance. Depending on the type of particle, they also have a long survival rate and can be inhaled by the next person entering the room.

Negative air pressurization

Negatively pressurized rooms are crucial in hospitals because this structure helps contain airborne pathogens. This theory has been tested multiple times, even historically with tuberculosis wards venting air to guinea pigs who became infected. Negatively pressured rooms have lower air pressure than the surrounding environment. This pressurization allows outside air in but doesn’t let any infected air out. This holds even when the door is opened. The air won’t flow out into the surrounding environment, thus risking contamination for others.


This stands for a nanometer and is a unit of measure. As part of the metric system, nanometers equal one-billionth of a meter. Even smaller than microns, this unit of measure is applied to atoms and molecules, the very basis of all matter. When it comes to measurements, a single water molecule is less than one nanometer. It’s also used to calculate ultraviolet light wavelength.

Positive air pressurization

Positively pressurized rooms are referred to as protective environments. These places are ideal for vulnerable patients who can’t be exposed to pathogens in a more volatile environment. These rooms are useful to control airborne spread when any visitors or staff could be potential carriers. This isolates people from any spikes in traffic or pathogens. These rooms maintain a higher pressure than the surrounding environment, so it won’t circulate back in when the air leaves the room. This allows the air leaving the space to be filtered, and bars entrance to outside pathogens and articles.


This name delineates between the disease and the virus . As a disease, the names COVID-19 and coronavirus disease are interchangeable. The name of the virus is severe acute respiratory syndrome coronavirus 2, which has been shortened to SARS-CoV-2. This differentiation is due to the difference between naming viruses and diseases. Viruses are named based on their biological and genetic structure. Diseases are called to focus on preparedness and response.


Part of this acronym stands for ultraviolet light. This type of light falls between visible light and X-rays, a particular wavelength that isn’t visible to the human eye. There are three different types of UV light. The light between 320-400 nm has a long wavelength and is called UV-A light. It’s often used for glow in the dark designs. UV-B light (290-320 nm) can cause sunburn. This type of light filters through the ozone in the earth’s atmosphere and causes skin cancer, cell damage, and sunburn. This is the type of light you’re trying to block out when you put on sunscreen. UV-C light, which falls between 100-290 nm, is harmful. This is because it destroys the nucleic acids in cells, which is very detrimental to human cells. This light is used as a disinfectant and is incredibly useful when contained and appropriately applied.


This abbreviation stands for ultraviolet germicidal irradiation . It’s a method of disinfection that relies on ultraviolet light to destroy microorganisms. These lights produce short-wavelength ultraviolet radiation that destroys DNA in microorganisms.Destroying the genetic material of these cells renders these microorganisms incapable of functioning or reproducing. However, this approach breaks down particles that can include eyes, human skin, and plastics. That’s why applying this approach is often best used in contained environments or upper-room UVGI. The success of this germicidal irradiation depends on the intensity, duration, and targeted microorganisms.

Viral kill dose

The effectiveness of germicidal irradiation is subjective to multiple factors. Efficacy is impacted by the duration and intensity of ultraviolet light. It also depends on the resistance of the microorganism being targeted and the type of environment. The power and time are what determines the viral kill dose. This informs how concentrated the dose of germicidal irradiation needs to be effective. Making sure that this viral kill dose is efficient is a huge priority when it comes to implementing continuous sanitation protocols in your building.


This acronym stands for volatile organic compounds . Certain solids or liquids emit these compounds as gases, and they often contain chemicals. These chemicals concentrate indoors, due to the vast number of products that they are present in. These compounds can be inhaled and cause long-term health problems, especially considering the overwhelming amount of time people spend indoors. These compounds are present in many household products, like paints, cleaning, and disinfecting problem. One of these compounds, for instance, is methylene chloride, which is converted to carbon monoxide in the body and is known to cause cancer in animals.