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RPME is the best practice to stop respirable dust

Jun 6, 2021

RPME is the Best Practice to Stop Respirable Dust

June 06, 2021

BreatheSafe Air Pressuriser System installed on a Komatsu PC490LC-11

RPME Respirable Particulate Mitigation Ecosystem:

A system, or group of interacting elements designed to protect the operator’s breathing zone environment

Bolting a pressuriser to a cabin without proper seals will not function well at all. Leaks in the cab will allow dust contamination to enter. The filters will be loaded by dust much sooner due to the higher volume (positive pressure) of air delivered to maintain a higher pre-set pressure (Positive pressure leakage).

The issues:

  1. A cabin by itself can no longer be assumed to resolve issues with respirable dust
  2. An environmental cabin serves as the primary method of dust control for operators for both surface and underground
  3. An environmental cabin/enclosure simply means that it can maintain a pre-set pressure level, for example: 20 pascals minimum.
  4. The effectiveness of the cab is maintained when the operator remains inside with doors and windows closed
  5. The HVAC must be well designed to cope with fresh air pressurisation (Hot/humid outside air)

BreatheSafe can assist with systems upgrades (Condensing) in very hot situations

  • The fresh air pressuriser is filtered with HEPA media to separate respirable dust
  • HEPA return air filters are fitted to control respirable dust inside the cabin (Particulate matter in shoes and clothes)
  • The benefit is HVAC internal components remain dust free; reducing unscheduled repairs and/or machine standing down due to failure.

Provisos:

– Auditing and testing the entire system

The cabin requires proper sealing to maintain positive pressure: Door and window seals must be replaced as soon as damage and/or leaks are detected.

WORK SMARTLY AND SAFELY

The best practice is to have a multitude of systems in place: Pre-cleaner and a fresh air HEPA pressuriser system matched to an environmentally sealed structure and which is pressurised to a controlled pre-set level. Procedures of sealing all gaps and making sure that window and door seals are in good working order are also required. The cabin must be kept clean always, with doors and windows remaining closed at all times.

Utilising a computer-controlled display system and citing an international standard such as EN15695 (Hazardous substances) is necessary as it states that the ideal pressure level is between 20 to 50 pascals for ONE person cabin. EN15695 imposes an absolute minimum: 20 pascals with a pressure display (Operator awareness) or 50 pascals without a pressure display.

Breathe-Safe system EN15695-4 system consists of:

  • Environmental cabin/enclosure (Tight against airborne particulate)
  • Pre-cleaner to expel coarse particulate (Extends the life of HEPA media)
  • HEPA filter forced ventilation (Fresh air pressuriser)
  • HEPA return air filter
  • Display (Operator awareness)
  • Remote Monitoring (Site management/maintenance)
  • Activated carbon media for Gaseous particulate
  • Fresh air volume minimum is 30m³/h for one person cabin to avoid CO2 build up

Exposure to respirable dust impacts worker health in the short and long term as well as on productivity for both man and machine. The other issue that needs to be understood is that fine dust does cause HVAC system contamination (HVAC internal restriction) over time and leads to unscheduled maintenance situations and other related issues such as underperforming climate control. The BreatheSafe ecosystem is effective at limiting respirable dust exposure to almost zero levels for the operator. Remote monitoring can be used for data management and systems review. It can also be used to provide training for operators where a window or door have been left open.

The conclusion is the sum of elements to protect the operator/s must remain effective over the entire lifecycle of the cabin/enclosure.

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DPM (Diesel Particulate Matter) is a group one carcinogen

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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

Jun 6, 2021

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.

Positive Pressure in Operator Cabins Not Enough

Positive Pressure in Operator Cabins Not Enough

Jun 3, 2021

 After conducting research and testing, BreatheSafe proposes a real-time dust monitoring study to evaluate the effectiveness of operator cabins working at mineral processing sites. This study focuses on bulldozers, front end loaders, and haul trucks. BreatheSafe evaluated that in order to keep cabin air safe with zero exposure, pressurisation of air was not enough. 

Demonstration of different sizes compared to a human hair at 50 - 70 microns in diameter.

Background

The belief that a machine cabin serves as a primary method for dust control needs to be reviewed. The risks associated with coal dust and silica dust exposure are now widely understood. Furthermore, there is scientific evidence which describes current worker exposure limits to low toxicity clouds of dust are not sufficiently protective. 

An environmental cab must control the air inside. It must be pressurised to keep outside dust from entering through cracks in the window and door. The pressurised air must be filtered to keep out dust-laden air from entering the cabin. To limit the volume of air needed for pressurisation, doors and windows must be sealed.

However, there is no standard or guidance on the actual efficiency of the filters. In fact, there is no real protection for operators regarding hazardous substances below PM10. Established research demonstrates particulate matter below PM10 can reach the deep tissue in the lungs.

The latest calls from health organisations is for silica dust to be undetectable within the breathing zone of the operator. The same must apply for all other airborne hazardous substances that are present at mineral processing sites.

Essentially, a cabin by itself can no longer be assumed to resolve these problems and could be in some instances be more harmful to the operator. The goal for any solution is to provide a Zero Harm environment, and this requires more than cab pressurisation.

Types of controls

ISO 10263

The standard for machinery sold in Australia has been ISO 10263. This standard provides for 50 pascals of positive pressure when the cabin is new, with a minimum of 25 cfm airflow intake into the cab. To achieve this design standard, the cab is equipped with a filtered fresh air intake system and a filtered recirculating system and an air conditioner.

The cabin is sealed by rubber gaskets, tight latches and jambs which are placed on windows and doors. The typical volume of a cab is approximately two to three cubic meters and utilizes pleated cellulose media.

OEM paper filters do not provide any protection for respirable dust, allowing PM10 pollution to enter unhindered.

This standard is fundamentally applicable to provide airflow to aid the air conditioning system. Other issues arise when both intake and recirculation airflow are powered by the same fan, changing a filter(s) media without correcting the resistance on the system will lead to cabin pressure loss.

Furthermore, this type of environmental cab deteriorates quickly due to fine dust ingress. Therefore, will become ineffective requiring a retrofit for effective fine dust particle separation.

EN15695-3

This standard refers to the control of hazardous airborne substances for the protection of the operator in tractor sprayers (pesticides). This standard states an environmental cabin must be tightly sealed and provide greater than 99% efficiency for the fresh air filter.

Fundamentally, the minimum requirement of EN15695-3 is tested and certified filter media to EN1822 (HEPA H13) which guarantees air filtration down to 0.3 microns.

High-Efficiency Particulate Air (HEPA) filters are made from randomly arranged glass fibres thus airflow will be highly restrictive. These cannot be easily adapted for replacing OEM paper filters.

Breathe Safe INPRESS TLProducts – BreatheSafe (breathe-safe.com.au)

The INPRESS TL system that has been developed and tested for mine sites to succeed EN15695-3. It uses dual HEPA filters rated to minimum 99.97% efficiency with Auto Cabin Pressure Control (ACPC). It also includes a digital display that alerts the operator when there is a low-pressure event. The next issue is cabin sealing to effectively isolate the air conditioning system and to also isolate the operator.

This system has been designed for coal mines to provide a Safe Breathing Zone for the operator. 

The cabin pressure setting can range from 20 to 100 pascals depending on the specific on-site requirements. Studies can be conducted to calculate dust load for a specific machine with remote monitoring.

Infographic for INPRESS TL system and how it works maintaining positive operator pressure and beyond. The INPRESS TL Cabin Pressuriser is mounted outside the cabin and clean the air with HEPA H13 filter. The Return Air Filter (RAF) isolates HVAC system and thrusts air out of vents creating safe breathing zone SBZ

Latest Guidance from Safe Work QLD (PN12377)

The following excerpt has been released form Worksafe Queensland for “Managing Respirable Dust Hazards in Coal-fired Power Stations for the Code of Practice 2018″

Isolation, segregation or enclosure of operations generating the dust

Relevant isolation controls include:

-Enclosed cabins with windows closed at all times

–Fitting high-efficiency air filtering systems (e.g. HEPA filters) to the intake and cabin recirculation air intake of front-end loaders, excavators and other machinery

-Keeping personnel vehicles dust sealed and pressurised.

We submit that a process of auditing of the cabin is included testing cabin sealing periodically and periodic testing with real-time dust monitoring instruments.

We also submit that machinery cabins be cleaned with a type H (HEPA) vacuum and never with brushes/brooms.  

Methods of Evaluation

EVADE

The latest technical support by The National Institute for Occupational Safety and Health (NIOSH) is to audit a cabin and/or the operator with a real-time dust monitor and a portable camera. This indicates events for high peak exposures that have occurred consequently prevent future events.