Air purification management in dental practice
Sterilization of instruments, disinfection of surfaces, precaution protocols have been mandatorily practiced in dental clinics. But air purification and aerosol management has not been routinely practiced. The importance of managing indoor air quality and aerosols to prevent cross infection and spread of infection has gained importance and debates have risen due to the ongoing Covid-19 pandemic.

Best practices for Aerosol Management

Steps for dental office air purification, as identified by the Environmental Protection Agency (EPA):

Source Control
Ventilation
Air Purification/ Air Cleaning
Dental clinics should not rely on a single precautionary strategy. A single step will reduce the risk of infection by a certain percentage. Infection control is additive, so adding extra protocols will reduce the potential risk.

Source Control

This involves minimizing the use of products, techniques and materials that cause aerosols and employing good hygiene practices to minimize biological contaminants. Uses of lasers, digital impressions, using hand instruments are some ways to avoid aerosols. However, certain procedures might demand use of aerosol generating methods. Thus, one needs to think on securing the work environment both for the dental clinic staff and the visiting patient.

Ventilation

The simplest form of mechanical ventilation is the use of exhaust fans, placed for instance in windows, to move air from inside a room to the outdoors. If exhaust fans are used, it is important to ensure that airflow is adequate, that air flows across the room (not in and out the same window or vent.

Air purification/ Air Cleaning

Air filters, electronic particle air cleaners and ionizers are often used to remove airborne particles and volatile organic compounds.

Benefits include:

Overall well-being and health of staff and dentists due to daily exposure
Patient health
Positive patient impression of the dental practice

Filters for Air purification

HEPA Filters
HEPA air filters are made from very tiny glass fibers that are made into a tightly woven paper. The filter consists of a numerous very small sieves that can capture extremely small particles, including some biological agents. They can remove at least 99.97% of dust, pollen, mold, bacteria, and any airborne particles with a size of 0.3 microns (µm). The diameter specification of 0.3 microns is the most penetrating particle size (MPPS). Particles that are larger or smaller are trapped with even higher efficiency. Pre-filters are used in air purifiers to prolong the life of the HEPA filter.

ULPA filters

Ultra-low particulate (or sometimes “penetration”) air (ULPA) filters are even more efficient than HEPA. ULPA filters are specified to remove 99.999% of contaminants 0.12 μm or larger in diameter

Types of HEPA Filters

Based on the efficiency European standards has classified the types of HEPA filters.

Classification    Filter type    Percentage efficiency at MPPS
E10    HEPA    ≥ 85
E11    HEPA    ≥ 95
E12    HEPA    ≥ 99.5
H13    HEPA    ≥ 99.95
H14    HEPA    ≥ 99.995
U15    ULPA    ≥ 99.9995
U16    ULPA    ≥ 99.99995
U17    ULPA    ≥ 99.999995
Table Source: AAF International

Consideration of standards and specifications

Commercially available air purifiers make claims with labels like HEPA-like, HEPA-type. It needs to be carefully evaluated because not all companies meet the required standards. Due to the false claims of HEPA-like or HEPA-type, manufacturers have come up with the term True HEPA and mentioning the particle size along with it. A buyer should evaluate the authenticity and check for standards set as per UN, EN or ISO standards.

Carbon Filters

They are highly adsorbent, forming a strong chemical bond/attraction to odorous, gaseous, and liquid contaminates, especially organic chemicals/compounds. Commercially available air purification systems incorporate carbon filters as a pre-filter to HEPA.

UV Light

The UV-C wavelength of 253.7 (254nm) nanometers has been proven to be effective at neutralizing (inactivating) microorganisms. Few of the commercially available air purification systems include UV light disinfection system in them.

Air purification technology

Ionization Systems

An ionizer is a device that disperses negatively (and/or positively) charged ions into the air. Negative ions magnetically attach to particles in the air giving them a negative (or positive) charge so that the particles may attach to nearby surfaces such as walls or furniture, or attach to one another and settle out of the air preventing it from being inhaled. However, there are certain safety cautions related to ozone being raised on systems soley based on Negative ionizer.

Plasmacluster technology

It produces positive and negative ions by using water vapor in the air. These ions actively attaches to pollutants and break down their surface before returning to air as water vapour.

Photocatalytic Oxidation

It is achieved when UV rays are combined with a TiO2-coated filter. This process creates hydroxyl radicals and super-oxide ions, which are highly reactive electrons and oxidises the pollutants.

Air purification – Technical parameters

Clean air delivery rate (CADR)

The clean air delivery rate, or CADR, is an important performance parameter for air purifiers. This numerical value will show us exactly how much of the specific particles to be removed from the air. The better CADR ratings are, the more powerful this air purifier’s fan is. Also, air purifier with high CADR ratings is having a high fan power to cover a large size of room.

Air Change Rate or Air Changes per Hour (ACH)

ACH stands for Air Changes per Hour. It indicates how many times per hour an air purifier device can exchange the air within a room. More fresh air exchange means better air quality in general. CDC defines a minimum of six air changes per hour (ACH) as criteria for an efficient ventilation system.

Final Note

Covid-19 pandemic has brought about changes in dental practice. In the present scenario, air purification has emerged to be a challenge to dental practitioners. With variety of products available in market, it is difficult to choose the best air purification system. Although there are no solid evidences on air purification being effective in preventing Covid-19 infection, using an air purifier can definitely be considered as a safety measure as part of infection control.