INAIL. A new approach in Air Duct Cleaning: the incapsulating method

Technical Consultancy for the Building Sector / INAIL Italian Compensation of Workers’ Autority / Corso di Porta Nuova, 19 20121 Milano, Italy+39 02 6258 60 48 / g.argento@inail.it

ABSTRACT

ABSTRACT

According to EU Directive nr. 89/391 regarding health and safety at work, the employers are obliged to keep under control the polluting concentration of the installation, further the threshold limits, the installation needs to be sanitized.

The European Norm 12097 provide requirements for maintenance of ductwork systems. INAIL has applied a new patented method (encapsulating), sanitizing ducts by polymeric resin aerosol, renovating the inner walls with only one operation.

Our aim is to show benefits of this new technology in an INAIL’s skyscraper. It has drastically been reduced the operations of the maintenance and provides a long-lasting antibacterial and antifungal environment.

Keywords

Keywords

IAQ, maintenance, antibacterial, sanitization methods.

INTRODUCTION

INTRODUCTION

According to the European and American organizations, in the industrial countries, people spend about 90% of their time within indoor and air conditioned places. The 30-40% of their time is spent in the workplaces.

Survey % of time spent at home% of time spent in otherconfinedenvironment% of time spent in transport means% of time spent outside

EPA –USA1 60 30 5 5

ISS/ANPA-

Italia253-64 13-28 - 17-24

(1) Environmental Protection Agency(2) Istituto Superiore di sanità / Agenzia Nazionale Protezione ambiente

Breathing pathologies are related rather to the Indoor Air Quality (IAQ) then the external atmospheric pollution. They think that 40% of absence from the workplace is mainly caused by the indoor air pollution because of an inadequate maintenance of the air conditioning ducts.

People are becoming aware of the air they breath especially in the workplaces where they stay more or less 8 hours. Usually in the office buildings we find the sources of pollution and related contaminants are following,

Unfortunately data concentration during an exposure period for 8 hours are not available in technical literature. The only data available are from CEN 1996 and ACGIH (American Conference of Governmental Industrial Hygienist ) issued in “Threshold Limit Values and Biological Exposure Indices”.

This exposure data have relevance also in the NIOSH “Sick Building” study (see chart below), where over 50% of problems comes in the buildings from an exposure to ventilations systems.

Problems affected by IAQ comes mainly from ductworks because of contaminants adhered on duct wall. This study will be focused on sanitation procedures used as an alternative cleaning methods. The principal goal is a renewal of the walls duct and cleanliness of surfaces then consequence.

DUCT CLEANING: TRADITIONAL PROCEDURES

The Air Duct Cleaning industry has increased over the years and offers several cleaning services. A first attempt to classify the air duct cleaning is provided by the European technical norm 12097:1999. According to the NADCA and ACE 2006 guidelines and regional laws, the cleanliness of internal duct surface is obtained by removing contaminants.

Traditionally the most popular method is a hand\mechanical (fig.1) removal, eitherby agitation devices (brushing) (fig. 4 and 5), or by contact vacuum (fig.2) or by the air sweep (fig.3) which uses an air blade to dislodge contaminants adhered on the duct walls. The last method is the most common and the most effective in improving IAQ.

Fig. 1 Mechanichal brush method (*)

Fig. 2 Contact vacuum method (*)

Fig. 3 Air sweep method (*)

(*) Source: “Cleaning Fibrous Glass Insulated Ducts,” North American Insulation Manufacturers Association

Fig. 4 Whirling brushes

Fig. 5 Whirling brush automated

In the first case the principle is a contact between the devices and any part of the ductboard. The limitation of this method depends on the shape, the size of the duct and, if exist on the interior fibreglass lined ducting. Some limitations derives from corrugated tubes (see fig.6) connected to the main duct with the air diffusers, and also comes when a part of the net is not accessible.

Fig. 6 Terminal corrugated tube

Fig. 7 Collom nozzles provide agitation to dislodging of debris

(Source: “Collom enterprises),

In the air sweep method some of these difficulties are reduced by an high air volume, outgoing from a nozzle (fig. 7) conveying the particulate (dust, dirt etc.) and microbial contaminants towards a lowest-pressure point.

The tools used are: compressors, vacuum pumps, pneumatic brushes, nozzles, airfiltration devices.

After dislodging the contaminants and after the vacuum device has captured any kind of contaminants, ductwork is considered cleaned, then the ductworks is disinfected by an Ultra Low Volume (ULV) device. Usually, the product inflating is either a biocide or a sanificant or a disinfectant. The product applied should has been chosen after visual inspection or a surface-test aimed to find out a microbial presence.

Even though several methods of duct cleaning are available, their effectiveness in reducing the level of airborne particulates in residential HVAC systems is unknown because there is a lack of established data and investigation. First of all we have to say that the maximum of contamination tolerable is 1g/m2 and when the walls of the duct are thoroughly hidden, by rule of thumb we can say that the amount of dirt is more o equal than 20 g/m2 and dust are stratified.

Talking about the most popular methods, cleaning ductworks by Mechanical Brush

Method and Contact Vacuum Method there is an electrostatic effect on the walls than, we are not sure to reach the value of 1 g/m2.

In 1994 the Building Construction Industry Advisory Committee (BCIAC - US)evaluated which duct cleaning traditional methods were effective against fibreglass and at which level they were effective in improving indoor air quality.

The research identified eight identical homes, where each couple of homes werechosen for a cleaning procedure and two homes ere used as study controls. Data and samples were collected both before during and after cleaning. Results are shown in fig 8.

Fig. 8 Comparison between the three methods in terms of fiberglass in 1 cm3

THE NEW APPROACH OF CLEANLINESS AND A CASE OF STUDY.

Recently has been developed a method which creates a new interface between the duct and the airflow. After the treatment, the grade of cleanliness is comparable to the most popular methods and has less dust on the walls.

We have two different patented procedures applied to the same method.

Anyone use a specific terminology, the first uses a manual procedure and a mobile atomizer (encapsulating), the second is totally computerized with fixed atomizer\s (regenerating).

The encapsulating method provides the air without fungi and bacteria andgives also new interface , instead the regenerating method realises a new interface.

Both methods should be adequately applied after a visual inspection\video survey and all the limitation listed above, regarding the traditional methods disappear.

The peculiarity of both the methods is a controlled, and uniform deposition of a resin into the duct by qualified workers without any dislodging process.

Some firms has developed the system avoiding any human intervention, calculating the deposition of polymeric atomization (fig.9, 10, 11) carefully created by air or inert gas, other use an airless spray system with high pressure (200 bars) to atomize the resin. Pressure and capacity and the tixotropic quality of the resin, contribute to realize the thickness of interface (200 µm), avoiding dripping. Some methods use a negative pressure in the ductwork which help air turbulence and avoid external spreading of contaminants.

Fig. 9 A single atomizer applied in a duct. A pipe is for resine another one is for gas

Source: RE.NOVA srl Italy

Fig. 10 The atomization process

Source: RE.NOVA srl Italy

Fig. 11 Two atomizer in progress placed side by side

(Source: RE.NOVA srl Italy)

In 1990 INAIL sanitized the HVAC system of a skyscraper, consisting of 13 handling air unit, supply systems and almost 6,000 m ductwork. The work aimed to improve IAQ because of a neglected maintenance for almost 40 years. Unknown date where the the real dimension of the ductworks, their spatial layout and the state of use. After a visual survey and the whole layout, it has decided to apply the encapsulated method, in this case dirt and all contaminants glued to the interior walls duct.

According to INAIL policy, this procedure grant an IAQ safe and provide a long lasting efficacy.

We will describe briefly all the steps. All the ducts need to be accessible and anyduct labelled in a hierarchical way. A daily plan procedure to encapsulate any duct has planned avoiding to forget something and to contaminate the indoor air. See the figure 12 and 13 of a vertical and sub horizontal duct when sanitization is work in progress.

Atomizer

Duct dirt

Pipe

Rail-guide

Duct sanitized

Fig. 12 Sanitization in progress of a vertical duct

(Source: INTEC srl Italy)

Rail-guide Duct dirt

Duct sanitized

Fig. 13 Sanitization in progress in a sub horizontal masonry duct

(Source: INTEC srl Italy)

THE PRODUCT

Usually use a specific resin for masonry, plastic and ferrous materials. It’s a styrol-acrylic based in water dispersion, with high and adhesive capacity, chemically resistant, inert even to microorganisms’ metabolism.

Formulated with inorganic pigments, free of lead, chromium and heavymetals, and with silicates with lamelliforme structure assuring the waterproofing power of coating. The main characteristic of the process are:

- it encapsulates and fixes to the walls dust material inside the ducts using aquick drying process and avoiding any cleaning operation;

- it excludes the risk of polluting materials dispersion in the environment;

- it dries quickly and forms an homogeneous white wall having a light flexibility which allows the absorption of eventual dynamic stress and vibrations.

Furthermore its low permeability to the steam protects the metallic walls of the ducts from oxidation phenomena;

- air flow in the treated ducts improves by 10%.

ADVANTGES AND DISADVANTAGES OF THE METHODS

The most important advantage of the new procedure, is to cover more then 98% of the duct surface by a uniform film (fig.14) without residual dust. Components of the resin affects elastics and hardness of the lining.

1 mm

Fig. 14 Scanning Electron Microscope image of duct walls (RE.NOVA ITALY)

An important advantage is that this process can be performed without interrupting the normal activity in the workplace without any risks for the working people and air conditioning system can work in a short time.

The most important characteristic of the polymeric film is the wettabilitywhich, allow to incorporate the particulate debris, rust and mould, mildew, bacteria, etc. onto the walls duct. The resin is also useful to solidify and reinforce ductboard or interior fibreglass lined ducting see fig.15.

Fig. 15 Examples of damaged fiberglass ductboard before and after the treatment (**)

Fig. 16 Example of rectangular duct pre and post encapsulating treatment (**)

Fig. 17 Example of circular duct, pre and post encapsulating treatment (**)

(**) Source: INTEC srl Italy)

HOW THE METHOD IS RELATED TO THE SAFETY AND HEALTH OF WORKERS

This chemical guarantees resistance against the proliferation of the most known and dangerous bacteria and fungi for many years (tests on ducts treated with this chemical after 9 years have confirmed the efficacy required) then it guarantees the non-toxicity for the operators and the users.

After testing the encapsulating product has obtained a recognition from the

Italian Ministry of Health, as a chemical which doesn’t interact with human body and has no free radicals. It is added in formula a biocide which is a non volatile organic molecule free from bactericides having toxic inorganic salt.

We can conclude that the product and the whole has an inhibiting activity and resistance against bacterial and fungi attack. A third part laboratory has certified that the efficacy of the product against the bacteria and fungi shown in fig.17 not only by suffocation caused by the coating action but also for chemical action.

Fig. 18 Bacteria and fungi on which the encapsulant product acts (**)

(**) Source: INTEC srl Italy)

ACKNOWLEDGMENTS

A special thank and appreciation to Mr. Edoardo TISI (IN-TEC srl – Segrate MI Italy)

REFERENCES

• 1. Agreement between Italian State and regions– Official bulletin n. 256 del 3 112006
• 2. Byron L. Ware ASCS, CIE, CMR          Use  and  application of sanifications in HVAC systems
• 3. Collom Enterprises, Inc. North America Dr  Buffalo,
• 4. ENV 12097\1999        Ventilation for buildings Ductwork Requirements for ductwork components to
• 5. European Directive of biological risk 90/679/CEE
• 6. INAIL       CONTARP     Il monitoraggio biologico negli ambienti di lavoro. Campionamento e analisi.
• 7. Italian decree n. 626\94
• 8. NADCA  –  General  specification  for  the  cleaning  of  commercial  heating, ventilating and air conditioning systems.
• 9. NAIMA    Facts  no.39.        Study  analyzes  effectiveness  of  duct  cleaning  in improving indoor air quality.
• 10. National Air Duct Cleaners Association ACR 2006 Assessment, Cleaning and Restoration of HVAC Systems 2006