(English version at rear part)
隨著新冠肺炎在世界各地持續爆發，各國對醫療口罩以及相關用品的連續需求，社區人群重用口罩的議題更顯成本效益。 就工藝層面而言，將用即棄式的3層外科口罩的外層和內層
(詳見：www.hkaac.net/post/mask-surgical) 之PP不織布改用織物，中間過濾層改為可更換式濾芯片，就有機會處理此項需求。大眾需改變習慣，就像日常生活中減少使用紙巾而改用織物手絹……
提示：有條紋向外，較彎曲一邊向上
政府近期公佈的銅芯口罩為6層設計：
--外層：採用氧化銅/棉紗構成的針織物，圓筒針織品一般具有良好的彈性，再輔以人體工學設計更容易包覆口鼻部分，
--內層：採用棉梭織物，吸潮濕，親和肌膚，內外2層織物經縫合成罩，可洗滌再用。開口式構建以供更換濾芯。外層採用氧化銅抗菌處理，其功能主要為抑制細菌和常見病毒，並可阻隔飛沫。使用金屬離子，如銀，銅，鋅等做抗菌纖維是業界採用已久的技術，但2014美國自然資源保護委員會(NRDC）鑑於銀會積累在人體內而限制納米銀在紡織品上的使用，現業界多轉用較安全的銅/鋅離子抗菌纖維。而主導的銅離子抗菌技術多適用於合成纖維，舉例：在熔融紡絲中加入氧化銅粉末到熔體，生產出含銅氧化銅顆粒並且均勻分佈的纖維其抗菌性能穩定而持久。推斷銅芯口罩外層針織物的用紗為帶銅基的聚酯纖維與棉作併線加捻/或包纏而成。
--(兩處)保護層：應可採用常規的PP紡粘不織布標稱20g/sq.M，主要做濾芯支撐；
--過濾層：常規採用PP熔噴不織布標稱20g/sq.M，但目前沒有CuMask 就此方面的近一步資料；
--抗菌層：可能採用了克重達65g/sq.M的PP不織布(據其提供給天祥的檢驗樣本)，經5%(重量/重量)氧化銅顆粒浸漬處理。
整個四層結構的濾芯，期望達到可洗滌60次。
總結：
-可洗滌再用口罩，只建議實施最基本的清洗，應留意洗滌標籤以保障有效性；
-做為可多次使用的口罩，(按常規材料推算)加厚了的濾芯，必然使配戴時的呼吸較常用的3層外科口罩為差，
-沒有文獻顯示氧化銅能消滅新冠病毒，(過濾功效以過濾層原料及工藝為主)，但引入氧化銅抗菌對多次使用型口罩有正面效果，該因社區人群並非長時間暴露於高濃度的新冠狀病毒飛沫(氣溶膠)，此為成本效益的選項。
Due to the COVID-19 pandemic, there is the continuous demanding of surgical masks and PPE (Personal Protective Equipment) globally. The issue of reusing masks in our community comes to be more cost-effective.
From the point of view of technical issue, concerning the:
outer and inner layers of disposable 3-layer surgical masks
(please refer to: www.hkaac.net/post/mask-surgical)
if we do some amendments:
- Replace the PP non-woven to textile fabrics,
- Re-design the middle filter layer by an interchangeable filter core, and then we can possible to tackle this issue. But the public needs to change a little bit in their daily life similarly to daring use less tissues and switch to textile handkerchiefs ...
Hints: with the strip-patterned side facing outward, put the curved edge upward
The CuMask recently announced by the Hong Kong government comes with 6-layer design:
-- The outer layer: knitted fabric made of copper oxide / cotton yarn. Since circular knitting fabric normally get good elasticity and it will secure fit your mouth and nose if further backup by ergonomic design.
-- The inner layer: skin-friendly cotton woven fabric to absorb moisture.
Both the inner and outer layer fabrics sewn together fabricate a cap and can be washed and reused. With the open-end construction for possibility of insect or remove filter-core-refill.The outer layer adopts copper oxide antibacterial treatment, capable of immobilising bacteria, common viruses and other harmful substances. The textile industry adopting metal ions such as silver, copper, and zinc as antibacterial fibers since years. In view possibility of silver will accumulate in the human body, 2014 Natural Resources Defense Council (NRDC) issue an order to restrict the use of nano-silver on textiles by 2014, since then the industry shift to the safer copper / zinc ion antibacterial fiber. Nowadays the mainstream technology of copper ion antibacterial is aim at synthetic fibers, say: adding copper oxide powder during melt spinning process to produce fibers containing copper oxide particles which relatively even distributed with stable and lasting antibacterial function. Hence we assume the outer layer of knitted fabric of the CuMask comes with copper-based Polyester /cotton double yarn or core-spun yarn.
-- (Two) Protective layers: possibly PP spunbond non-woven with nominal 20g / sq.M, which functioning as the filter support;
-- The filter layer: conventionally the PP melt-blown non-woven with nominal 20g / sq.M will be applied. For CuMask if any special know how?
-- The anti-microbial layer: may use PP non-woven with a weight of 65g / sq.M （according to the sample submitted to Intertek）and impregnate with 5% (wt/wt) Copper oxide particles.
The entire four-layer filter element is expected to be washed 60 times.
Conclusive:
- Washable reusable masks, should only undergo the very basic cleaning, pay attention to the care label to ensure its effectiveness;
- As a reusable mask, with thickened filter element (base on the assumption of conventional materials) will inevitably make the wearer get less comfortable when compare to those 3-Ply surgical mask.
- There is no literature indicating that copper oxide can eliminate the COVID-19 virus (the filtering effect is very much depend on the raw material adopted as well as the mechanism of the filtering layer), but the introduction of copper oxide antibacterial treatment gain positive for those reusable masks, as long as the community is not exposed to high concentrations of COVID-19 droplets (aerosols) constantly, hence it will be a cost-effective option.