A ventilation system made of copper is a guarantee of aesthetics, durability and low cost of operation. Such an installation, apart from its unique style and colour, is also very durable. It does not undergo corrosion; moreover, it is resistant to changes in atmospheric conditions and air pressure in the installation.
The characteristics of copper perf
ectly match the needs of users of ventilation systems. Copper is an excellent conductor of heat and electricity. Additionally, in a natural way, it prevents the growth of bacteria.
Copper, thanks to its properties, is very durable and plastic. In contact with moist air, a layer of patina is formed. Copper reacts with air containing water vapour, is susceptible to fresh well-oxygenated water, but does not react in contact with seawater.
The following have a strong effect on copper:
Copper dissolves in nitric acid. Copper has a high resistance to temperature and pressure fluctuations. Additionally, it is non-combustible.
Thanks to its biostatic properties, copper inhibits the growth of bacteria. Research approved by the EPA (Environmental Protection Agency of the United States) proves that copper destroys harmful bacteria, germs, microbes, pathogens, moulds, fungi and viruses that come in contact with the surface of copper ducts. In addition, a copper ventilation installation is much safer than a steel installation that must be regularly cleaned using ozone and chemical biocides.
The bactericidal function of a material, what do we mean by this? The bactericidal function of material means the ability to inhibit the growth of a wide range of micro-organisms such as bacteria, moulds, fungi, viruses and yeasts on a given surface. When exposed to bacteria on copper surfaces the material exhibits germicidal properties, this is confirmed by Environmental Protection Agency (EPA) studies.
In the table below we can see the different types of bacteria applied in a specific way to copper and the time of their inactivation.
Through these observations, the following conclusions can be drawn: higher temperature and higher relative humidity increase the effectiveness of contact killing. Treatments that reduce the corrosion rate, e.g. the use of corrosion inhibitors or a thick layer of copper oxide, reduce the antimicrobial effectiveness of copper surfaces.
Tabel 1. Contact killing of microbes by copper surfaces
| Species | Application method | Killing time, RTa |
| Salmonella enterica | Wet, 4.5 × 106 CFUb | 4 h |
| Campylobacter jejuni | Wet, 4.5 × 106 CFUb | 8 h |
| Escherichia coli O157 | Wet, (3-4) × 107 CFUc | 65 min |
| Escherichia coli O157 | Wet, 2.7 × 107 CFUc | 75 min |
| MRSAd (NCTC10442) | Wet, (1-1.9) × 107 CFUc | 45 min |
| EMRSA-1e (NCTC11939) | Wet, (1-1.9) × 107 CFUc | 60 min |
| EMRSA-16e (NCTC13143) | Wet, (1-1.9) × 105 CFUc | 90 min |
| Listeria monocytogenes Scott A | Wet, 107 CFUc | 60 min |
| Mycobacterium tuberculosis | Wet, 2.5 × 107 CFUf | 5 to 15 daysg |
| Candida albicans | Wet, >105 CFUf | 60 min |
| Klebsiella pneumoniae | Wet, >107 CFUf | 60 min |
| Pseudomonas aeruginosa | Wet, >107 CFUf | 180 min |
| Acinetobacter baumannii | Wet, >107 CFUf | 180 min |
| MRSA | Wet, >107 CFUf | 180 min |
| Influenza A virus (H1N1) | Wet, 5 × 105 virusesh | 6 h, 4-log decrease |
| C. difficile (ATCC 9689) vegetative cells and spores | Wet, 2.2 × 105 CFUc | 24-48 h |
| C. difficile NCTC11204/R20291 vegetative cells | Wet, (1-5) × 106 CFUi | 30 min |
| C. difficile dormant spores | Wet, 8 × 106 CFUi | Unaffected in 3 h |
| C. difficile germinating spores | Wet, 8 × 106 CFUi | 3 h, 3-log decrease |
| Pseudomonas aeruginosa PAO1 | Wet, 2.2 × 107 CFUj | 120 min |
| MRSA NCTC 10442 | Wet, 2 × 107 CFU | 75 min, 7 log decrease |
| Escherichia coli W3110 | Dry, 109 CFUi | 1 min |
| Acinetobacter johnsonii DSM6963 | Dry, 109 CFUk | A few minutes |
| Pantoea stewartii DSM30176 | Dry, 109 CFUi | 1 min |
| Pseudomonas oleovorans DSM 1045 | Dry, 109 CFUk | 1 min |
| Staphylococcus warnerii DSM20316 | Dry, 109 CFUk | A few minutes |
| Brachybacterium conglomeratum DSM 10241 | Dry, 109 CFUk | A few minutes |
| Aspergillus flavus | Wet, (2-300) × 105 sporesc | 120 h |
| Aspergillus fumigatus | Wet, (2-300) × 105 sporesc | >120 h |
| Aspergillus niger | Wet, (2-300) × 105 sporesc | > 576 h |
| Fusarium culmonium | Wet, (2-300) × 105 sporesc | 24 h |
| Fusarium oxysporum | Wet, (2-300) × 105 sporesc | 24 h |
| Fusarium solani | Wet, (2-300) × 105 sporesc | 24 h |
| Penicillium crysogenum | Wet, (2-300) × 105 sporesc | 24 h |
| Candida albicans | Wet, (2-300) × 105 sporesc | 24 h |
| Enterococcus hirae ATCC 9790 | Wet, 107 CFUc | 90 min |
| Different Enterococcus spp. | Wet, 106 CFUf | 60 min |
| Candida albicans | Dry, 106 CFUk | 5 min |
| Saccharomyces cerevisiae | Dry, 106 CFUk | 30 s |
a RT, room temperature; only the values for the most efficient alloy are reported.
b Inoculation with 1.5 ml of culture (4.5 × 106 CFU), kept under humid conditions.
c Inoculation with a 20-μl drop of culture.
d Methicillin-resistant Staphylococcus aureus.
e Epidemic methicillin-resistant Staphylococcus aureus.
f Twenty microliters of culture spread on coupons.
g Time before strain became culture positive in Bactec 12B growth medium after exposure to copper.
h Inoculation with 20 μl of virion suspension.
i One hundred microliters of dilute culture.
j Twenty-five microliters of culture spread on coupons with a glass spreader.
k Thin film applied with a cotton swab.
The mechanism for killing bacteria is shown in the figure below.
FIG. 1. Cartoon of the tentative events in contact killing. (A) Copper dissolves from the copper surface and causes cell damage. (B) The cell membrane ruptures because of copper and other stress phenomena, leading to loss of membrane potential and cytoplasmic content. (C) Copper ions induce the generation of reactive oxygen species, which cause further cell damage. (D) Genomic and plasmid DNA becomes degraded.
The bactericidal properties of copper are of continuous interest to scientists. Research and analyses are conducted on various applications of this material, e.g. in hospitals, public buildings, public transport. Everywhere where there is a risk of bacterial concentrations.
Additionally, copper conducts heat very well, thanks to which this material is ideal for installation for heat exchangers. Copper installations are a good choice for places exposed to seawater as they do not react with saline.
Ventilation ducts and fittings also can be made of copper - thus, they take the natural antibacterial properties of the material. Copper ductwork is made in the same technology as traditional spirally wound galvanized SPR-C ducts. Available diameters range from 100 to 500 mm, including all intermediate dimensions produced from a material of a thickness of 0.5
mm.
Check technical data for spiral ducting
Segment fittings that are connected to pipes by means of male couplings can also be made in a system with EPDM seals, providing an increased airtightness class. Copper bends, T-pieces, reducers, and ventilation nozzles are made in segments of dimensions compatible with galvanized fittings.
Copper roof cowls match perfectly roofs made of this material; they both change colour during the oxidation process. Thanks to this, roof edges will form a coherent whole.
In addition to the functional properties of copper ventilation elements, the characteristic colour of copper is also worth noting. Thanks to it, copper ducting adds uniqueness to the design of modern lofts and stylish retro interiors.
References:
1. Metallic Copper as an Antimicrobial Surface Gregor Grass, Christopher Rensing, Marc Solioz Appl Environ Microbiol. 2011 Mar; 77(5): 1541–1547. Published online 2010 Dec 30.