Five Common Misconceptions about Air Filters

Five Common Misconceptions about Air Filters

Five Common Misconceptions About Air Filters

September 20, 2021

There’s lots of information out there about air filters, particularly in the time of COVID-19. But for industrial air filtration and pressurisation in hazardous environments, we find the same misconceptions popping up repeatedly.

1) Cabin pressure is enough to protect operators

Positive pressure does keep hazardous dust from entering into the cab through tiny openings. However, it doesn’t stop hazardous dust from entering the cabin. Ambient air is pumped into the cabin to create a positive pressure difference between inside and outside. This ambient air, however, still contains all of the harmful airborne particulates outside!

By filtering this fresh air, purified and clean air enters the cabin and blows into the operator breathing zone.

2) Air filters will restrict airflow in the vehicle

In traditionally designed pressurisers, the higher the efficiency class of your filter, the less airflow entered the cabin. This is why many brands market MERV-16 or EPA filters as the optimal combination between airflow, price and filtration efficiency.

However, BreatheSafe High Pressure Filtration systems can maintain appropriate airflow, even with higher classes of filtration. As standard, we sell HEPA H14 filters in our pressure systems. We believe that filtration is a significant factor in protecting the enclosed area from hazardous dust. This airflow is capable because of the brushless motors and advanced intelligent motor power control of in-cabin pressure.

3) HEPA air filters are only 99.99% effective

HEPA classification works on its effectiveness in filtering particles at the Most Penetrating Particle Size (MPPS). Particles of approximately 0.3 μm – the MPPS – are the hardest to catch. The size at which the air filter has its lowest arrestance value and penetrates through filtration processes at the most common rate. For this reason, the European standard EN 1822 assesses the filtration performance of the filter by measuring the penetration of 0.3 μm sized particles. Much smaller nanoparticles are easier to catch.

Tests conducted by NASA showed that HEPA filters are highly effective in capturing up to 100% of nanoparticulate contaminants and larger particles greater than 0.3 μm. However, for particles around the MPPS, there is a tiny drop in filtration efficiency.

Classic Collection Efficiency Curve with Filter Collection Mechanisms

According to EN 1822, a HEPA filter must remove at least 99.95% of particles sized 0.3 μm or larger. US government standards require a filter to remove 99.97% of particles sized 0.3 μm to qualify as HEPA.

That is why HEPA filters are actually more than 99.99% effective at removing hazardous particles from the air but are rated as so. These MMPS particles are still dangerous, which is why the higher the %, the better it is for your health.

4) Replace air filters when they look dirty

A common question we receive is, isn’t replacing filters expensive?

We’ve found that many customers are replacing their filters well before they are full. It is particularly worrying because the fuller a filter is, the more effective it is. Our INPRESS system includes automatic motor power control that increases when pressure within the cabin decreases. Cabin pressure decreases over time due to the filter filling up, and when the INPRESS sees it getting lower, it increases blower speed to maintain the pressure setpoint. In addition, the INPRESS will let you know when the filter is too full when the motor is going at excessive speeds. This extends filter life and prevents early changing, saving you money.

With motor control, it also blows through lower volumes of air to maintain that pressure, meaning less debris and the particulate matter goes through the filter, filling it up slower. We have introduced a new touch screen display that shows in real-time the capacity of our pressuriser, which means sites will know when to replace filters! That’s a cost-saving that can be multiplied by all the machines equipped with BreatheSafe systems.

BreatheSafe HEPA filter after 2800 hours of use, and still effective

5) An air filter will heat up the cabin

Traditional pressuriser designs run their motors at 100% consistently to maintain airflow, resulting in a noisy, hot machine and atmosphere. An uncomfortable operator enclosure can result in untrained operators winding down windows for fresh air, letting all the hazardous particles inside.

However, we design BreatheSafe High Pressure Air Filtration systems to blend with the machines pre-existing airconditioning system, so the fresh, clean air is cooled before entering the cabin. Beyond that, our motors run with minimal power and still provide substantial airflow, maintaining a comfortable enclosure in even the hottest environments.

How many of these misconceptions did you believe? Let us know!

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In 2018, BHP consulted with BreatheSafe concerning airborne mine dust mitigation for their Autonomous 793F trucks. A field trial was started to deliver a full system to mitigate airborne dust, heat and water ingress with their Caterpillar fleet of Autonomous Trucks – electrical cabinet.

The Problem

The ongoing issue is airborne mine dust: there is dust build-up inside the electrical cabinet. This is causing electrical systems to run hot due to dust accumulation and electrical connections to corrode and fail when contaminated with abrasive particles. Airborne mine dust can comprise different materials that affect components with abrasive and corrosive properties.

Also, temperature control issues are critical in enclosure design. When temperature increases, it will affect electrical components. The optimal temperature for most electrical equipment is between 40⁰C to 50⁰C. Thus, when the internal temperature of electrical components rises above the optimal range, then their lifespan will decline. Further complication is OEM electrical cabinet has a small opening door which makes servicing difficult and time consuming


The Solution

BreatheSafe custom design insulated cabinet enclosure: equipped with HEPA fresh air pressurisation integrated with temperature sensing and active cooling plus large access door; the key features are:

  • Keeps electrical components dust free.
  • Dramatically reduced maintenance costs.
  • Active cooling maintains enclosure internal temperature below 50⁰C.
  • Automatic Pressure Control (positive pressure is always maintained).
  • Remote monitoring: ongoing data for temperature and positive pressure.
  • Long life brushless electrical motor.
  • HEPA filters mitigate dust particulate down to submicron level.
  • Large door makes easy access to internal components.
  • No tools required for all dust mitigation system servicing.
  • Full service back up

The Result

BreatheSafe autonomous cabinet enclosure can effectively control airborne dust down to submicron level with active cooling program. As soon as temperature rises above 45⁰C then pressuriser motor goes into high speed to cool enclosure effectively maintaining below 50⁰C.

Remote monitoring data has assisted with maintenance schedule routine with real time data for dust loading calculation.

Auto pressure control maintains positive pressure inside enclosure regardless of wind speed or as vehicle moves forward. Engine air pre-cleaner ejects coarse dust to successfully extend HEPA filters lifecycle.

Trial success, BHP has placed order to convert fleet to BreatheSafe custom enclosure.

OEM cabin filters were not designed to stop respirable dust

OEM cabin filters were not designed to stop respirable dust

OEM cabin filters were not designed to stop respirable dust

June 06, 2021

*OEM filter media is not designed to mitigate respirable dust.

Dust inside OEM airway immediately AFTER filter.

Fine dust contamination is the main reason for air conditioning-HVAC system underperformance and premature failures. Dust wears out electrical components quickly while dust accumulation inside the system restricts airflow increasing the entire system heat load.

This is due in part to the inefficacy of OEM filters and the harsh and dusty conditions at mine, quarry and construction sites

The design of the original HVAC system by the manufacturer is intended to deliver cooling capacity overall and may not be designed to perform in extremely dusty environments or to be effective at removing smaller fine dust.

The OEM filters are normally intended to filter out coarse dust but not hazardous respirable particulate.

OEM filter from a Volvo EC480 and a CAT 972H

OEM filter from a Volvo EC480 and a CAT 972H

For instance, if HEPA filters were to be retrofitted to an original system, the end result is a system that may not be capable to cool down the cabin from higher air restriction of HEPA filters. The best practice is to use a multitude of controls combined with an environmental cabin (tight against particulate) that is precisely designed with fresh air pressurisation with HEPA filters to control respirable dust.

The BreatheSafe design is a custom system that regulates the correct volume of fresh air delivered to the air conditioning- HVAC system. Thus, minimise the amount of hot ambient air being blown into the cabin – reducing the heat load on the HVAC. The system can effectively keep the operator comfortable even in very hot and humid conditions.

The worst scenario is an air conditioning-HVAC system that is not effective at cooling the working environment leading to unsafe practices such as the operator opening a window for ventilation risking high exposures and allowing the cabin to be contaminated with respirable dust. This situation is hazardous because once respirable dust is inside the cabin; it will continue to be recirculated by the air conditioning system.

This BreatheSafe system has been installed with HEPA primary and HEPA return air filter for equipment working at a cement shed with 8000 hours of operation. It has kept the cabin clean and it has kept the internal HVAC components clean and dust-free.

*Some OEM’s offer a HEPA option.

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Aerosol & DPM: controlling hazardous submicron respirable particles

At mineral processing sites, there are lots of substances that can remain airborne for days depending on the size of the particulate matter (PM).

There are sites that must mitigate against sulphur dioxide and other toxic gases with mild to dangerous health effects depending on concentration.

The emerging issue is diesel exhaust emissions emissions which are classified as DPM (Diesel Particulate Matter) these may be the some of the most hazardous exposures at underground mines and above ground operations. The composition of diesel particulate matter is complex and the reason that there is so much potential risk to health.

Diesel exhaust includes more than forty substances that are listed as hazardous air pollutants and fifteen are listed as carcinogenic to humans.

Furthermore, chemical reactions in the atmosphere contribute to secondary particulate matter reactions; again, with carcinogenic properties. Diesel combustion particles are made up of fine particles (PM 2.5) combined with a high level of ultrafine particles (PM 0.1) The particulate that is in the PM2.5 range deposit in the deep tissue of the lung exactly where the human body is not able to expel these.

The fraction at PM 0.1 has been shown to cross from airways into our bloodstream.

The solution is well ventilated areas with isolation measures and the best practice is to utilize a multitude of controls. An environmental cabin / enclosure equipped with fresh air pressurisations is the best practice to ensure a safe work environment for the operator (Doors and windows must remain closed always).

The cabin / enclosure must be installed with HEPA filtration to separate airborne fine particles.

The cabin / enclosure must also be equipped with an activated carbon filter phase to adsorb airborne ultrafine particles.

Sites in Western Australia utilising HEPA filters in a fresh air pressurised cabin have halved their exposure values.

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Silica (RCS) is twenty times more toxic than coal dust

Silica (RCS) is twenty times more toxic than coal dust

SILICA (RCS) respirable crystalline silica

Respirable mine dust in high concentrations cause lung disease due to overloading the defences of the respiratory system as particles start to deposit in the lung.

Silica airborne particles are 20 times more toxic to the lungs than coal dust alone; nevertheless, Silicosis is the world’s oldest known occupational disease. Workers who are exposed and inhale invisible Silica (RCS) particles are at increased risk of developing serious – and often deadly – silica related disease.

In the United States the Mines Safety and Health Administration (MSHA) has introduced a new rule that has lowered the concentration limit for respirable coal dust from 2.0 mg/m³ to 1.5 mg/m³.In regard to Silica the Occupational Safety and Health Administration (OSHA) new rule has been brought in and is expected that MSHA will follow suit. The new limit from OSHA’s new rule cuts the permissible exposure limit (PEL) in half from 100 to 50 micrograms (as an 8-hour time weighed average)

HEPA filtration system is effective at controlling respirable dust exposure as long as the operator remains inside.

The health risks associated with exposure to RCS can be controlled with the use of effective systems installed in environmental cabin/enclosures to isolate workers. Respirable crystalline silica (RCS) is one of major issues brought to the attention of the Queensland Parliament – Coal Workers’ Pneumoconiosis Select Committee Inquiry. The select committee will be looking at evidence of silica exposures of Brisbane’s tunnel workers.

“Silica is probably more dangerous than coalmine dust. We talked about the toxicities earlier. Quarriers, tunnelers, metal miners—anyone who is disturbing the earth’s crust and drilling through rock is at risk for quartz and silica exposure. There should be industrial hygiene monitoring of the exposure levels. We just lowered our exposure level to silica from 0.1 milligram per metre cubed to 50 micrograms or 0.05 milligrams per metre cubed because of the horrendous diseases that occur from silica.

Aside from the diseases we have already talked about for coalmine dust, silica is actually a lung carcinogen. It is an International Agency for Research on Cancer, IRAC, class 1 human carcinogen. It causes renal disease and causes other autoimmune diseases like rheumatoid arthritis and other things.”

Dr Cohen

To mitigate exposure to respirable dust a multitude of controls must be used. Then it should follow that fresh air pressurisation systems should be installed with HEPA filters in a two-stage setup: primary and return air stages to filter outside fresh air and also to filter the air that is inside the enclosure to same HEPA standard.

This process maintains the HVAC system dust free thus extending the lifecycle of the system and maintains the cooling capacity by avoiding air restrictions caused by dust contamination. These aspects must be considered, as it will result in costs reduction over the service life of the system. Specifically, reduce the overall costs of servicing & repairs of the HVAC system due to dust ingress contamination.

Finally, Its widely known and common practice that respirable fibres (Asbestos) must be removed using HEPA vacuum cleaners. The same principle applies in controlling respirable particulate inside the cabin.

Find out more about HEPA fresh air pressurisation technical guide.