The complete evidence base behind Spero’s EMF shielding claims — measurement standards, fabric performance data across the full RF spectrum, material science, wash-durability research, and independent lab certifications. Every claim is documented and cited.
Spero Protection Clothing is made from premium silver-fiber, copper-nickel, and stainless-steel shielding fabrics sourced from established conductive-textile manufacturers with over 20 years in the silver-fiber industry. These are the same fabric families used in commercial anti-radiation apparel, industrial EMC shielding, and conductive workwear worldwide.
Every fabric is independently tested by the supplier’s certified laboratory using internationally recognized methods: ASTM D4935-10 (coaxial transmission cell, 30 MHz to 18 GHz) and IEEE Std 299-2006 (aperture method, 800 MHz to 12 GHz). Test results are published as frequency-by-frequency attenuation curves for each fabric — the same documentation format used across the global EMC shielding industry.
Spero’s shielding fabrics block between 90% and 99.9999% of electromagnetic radiation depending on the specific fabric and frequency, with our highest-performing fabrics (used in Faraday bags) reaching 60–70 dB of attenuation across cellular, Wi-Fi, and Bluetooth bands.
Spero sources the TEXCARE detergent under license from YShield (Germany) — a specialized formula designed specifically to preserve silver-fiber conductivity during washing, with zero enzymes, bleach, optical brighteners, or chlorine.
This document presents the complete evidence base for Spero’s shielding claims: measurement protocols, fabric performance data across the full RF spectrum, material science, wash durability research, safety guidance, and answers to the most common questions — all with cited sources.
Two internationally recognized methods govern electromagnetic shielding measurement for textile materials.
ASTM D4935-10 uses a coaxial transmission-line cell (TEM cell) to measure how much electromagnetic energy passes through a fabric sample across frequencies from 30 MHz to 18 GHz. The test is polarization-independent — the fabric’s orientation does not affect the result. This is the primary standard for measuring the shielding effectiveness of flat textile materials [1].
IEEE Std 299-2006 uses a shielded enclosure with a 40 cm × 40 cm aperture. Horn antennas are positioned at standardized distances (84 cm transmit, 30 cm receive), and the fabric sample covers the aperture. This method tests from 800 MHz to 12 GHz and closely approximates real-world garment shielding conditions [2].
Think of it this way: ASTM D4935 tells you how well the fabric itself blocks signals. IEEE 299 tells you how well the fabric performs when it is covering an opening — closer to how a garment actually works on a body.
Spero’s fabric suppliers operate certified in-house testing laboratories that conduct shielding measurements on every production lot. Test data is published as a fabric specification sheet showing attenuation in decibels at standardized frequencies from 1 GHz to 18 GHz. Spero retains a complete specification sheet for every fabric used in our products and makes the underlying numbers available through this document.
For independent verification, an RF measurement using a calibrated EMF meter (such as those made by Gigahertz Solutions, Cornet, or TinySA) can confirm the shielding performance of any Spero garment against ambient RF sources in the home or workplace.
Beyond shielding performance, Spero’s core silver fiber has been tested for chemical safety by SGS — one of the world’s largest independent testing, inspection, and certification companies — not just by the manufacturer’s in-house lab. Three SGS reports are on file:
These reports cover the silver filament and the SCN003 100%-silver-fiber fabric specifically. Copies are retained on file and available on request.
Decibels (dB) measure shielding on a logarithmic scale — like earthquake magnitudes. Each 10 dB increase means 10 times more blocking power [3]:
| Attenuation | Percentage Blocked | What It Means |
|---|---|---|
| 10 dB | 90.0% | Blocks 9 out of 10 units of energy |
| 20 dB | 99.0% | Blocks 99 out of 100 |
| 30 dB | 99.9% | Blocks 999 out of 1,000 |
| 40 dB | 99.99% | Blocks 9,999 out of 10,000 |
| 50 dB | 99.999% | Blocks 99,999 out of 100,000 |
| 60 dB | 99.9999% | Blocks 999,999 out of 1,000,000 |
For context: a concrete wall provides roughly 10–15 dB of attenuation. A single layer of Spero’s heaviest blanket fabric provides over 50 dB — more than 1,000 times more shielding than a concrete wall.
Each Spero product category uses a specific fabric chosen for its shielding profile, comfort, weight, and care requirements. The table below summarizes the measured shielding effectiveness of our fabric families at 1 GHz (representative of cellular and Wi-Fi bands), with the full range across 1–18 GHz shown for context.
| Fabric Family | Used In | @ 1 GHz | Range (1–18 GHz) | Composition |
|---|---|---|---|---|
| Premium Silver Tricot | Maternity, baby, kids’ headwear, slip dress, sleep mask | 54 dB / 99.9996% | 45.7–58.6 dB | 100% silver fiber, warp knit |
| 4-Way Stretch Silver | Belly band back layer | 47 dB / 99.998% | 38.9–47.5 dB | 62% silver / 38% spandex |
| Calendered Silver Ripstop | Faraday bag inner layer | 59 dB / 99.99987% | 47.8–59.9 dB | 100% silver fiber, ripstop woven |
| Silver Woven Twill | Faraday bag outer layer | 56 dB / 99.99975% | 46.7–61.7 dB | 57% silver / 43% viscose |
| 3D Air Multilayer Silver | Hoodies, sweatpants, baby beanie | 34 dB / 99.96% | 14.1–33.9 dB | 26% silver / 51% cotton / 23% polyester |
| Silver-Cotton Blend (Heavy) | Leggings, headband | 37 dB / 99.98% | 24.1–48.0 dB | 57% silver / 37% cotton / 6% spandex |
| Silver-Cotton-Nylon Blend | T-shirts, tank tops, shorts, briefs, toddler beanie | 34 dB / 99.96% | 20.4–34.2 dB | 44% silver / 35% cotton / 18% nylon / 3% spandex |
| Silver Interlock Knit | Grounding mat | 35 dB / 99.97% | 19.5–35.1 dB | 55% silver / 45% nylon, interlock |
| Premium Blanket Fabric | Throw blankets | 55 dB / 99.99968% | 37.9–55.1 dB | 53% silver / 47% polyester woven |
| Conductive Anti-Radiation Twill | Sleep sack | 40 dB / 99.99% | 14.4–40.2 dB | 11% silver / 89% cotton twill |
| Earthing Fabric | Grounding sheets | 22 dB / 99.4% | 0.4–21.5 dB | 6% silver / 94% cotton (designed for grounding, not shielding) |
| Copper-Nickel Mesh | Faraday bag outer reinforcement, key fob | 60–70 dB / 99.9999–99.99999% | — | Copper-nickel plated weave |
| Silver Fiber Mesh | Mesh hood panel | 53 dB / 99.9995% | 38.9–55.0 dB | 100% silver fiber, open mesh (34 g/m²) |
| Direct-Knit Silver | Socks, texting gloves | ~25 dB / ~99.7% | 20–30 dB | Knitted directly (like socks); too small for standard lab fixture |
Spero’s Faraday bags (5G Phone Protection, 5G Radiation Pouch, X-Large Faraday Bag, iPad Faraday Protection, Key Fob Faraday Bag) use a multi-layer construction combining two or three of the fabric families above. The composite shielding exceeds the performance of any single layer. Tested signal isolation reaches 60–70 dB across cellular (700 MHz – 5.8 GHz), Wi-Fi (2.4 + 5 GHz), Bluetooth (2.4 GHz), and GPS (1.5 GHz) bands — effectively eliminating signal transmission through the bag.
| Wireless Technology | Frequency | Premium Silver Tricot | Silver-Cotton-Nylon Blend |
|---|---|---|---|
| 4G / GSM 900 | 900 MHz | ~58 dB (99.9998%) | ~38 dB (99.984%) |
| 4G / GSM 1800 | 1.8 GHz | ~56 dB (99.9997%) | ~34 dB (99.96%) |
| Wi-Fi | 2.45 GHz | ~57 dB (99.9998%) | ~33 dB (99.95%) |
| 5G sub-6 | 5.8 GHz | ~58 dB (99.9998%) | ~31 dB (99.92%) |
| Radar / X-Band | 9.5 GHz | ~55 dB (99.9997%) | ~25 dB (99.7%) |
A consistent pattern holds across all our fabrics: shielding effectiveness is highest at the lower frequencies most relevant to cellular and Wi-Fi exposure (1–3 GHz), and remains strong through the 5G sub-6 band. Even at 5.8 GHz the premium fabrics still block over 99.99% of electromagnetic energy.
Our grounding sheets and grounding mat are designed for earthing — providing a low-resistance electrical path from your body to a ground connection — rather than as RF barriers. Earthing fabrics use less silver (sufficient for conductivity) and prioritize comfort and breathability over raw shielding. The grounding mat (35 dB) does provide secondary RF shielding when in contact with your body; the grounding sheet (22 dB) is optimized for earthing function rather than shielding. Both products serve a different purpose than our shielding apparel.
Silver-fiber fabrics are produced through one of two manufacturing approaches.
Chemical Plating: A base fabric — typically nylon or polyester — is coated with a layer of high-purity silver through an electroless chemical deposition process. The silver bonds directly to the fiber surface, creating a conductive layer. This approach yields lightweight fabrics with high conductivity, ideal for garments where the silver is on the interior surface and protected from direct skin contact.
Spun Yarn With Silver Content: Silver fibers are blended with natural or synthetic fibers (cotton, nylon, polyester) at the spinning stage, creating a yarn with silver distributed throughout. This approach yields fabrics with softer hand-feel and more even silver distribution, suitable for shirts, tank tops, and other direct-skin-contact garments.
Spero uses both manufacturing approaches across the product line, with the choice driven by garment use case (skin contact, durability, breathability) and shielding requirement.
Silver has the highest electrical conductivity of any element, exceeding copper by approximately 6% and aluminum by 60%. This conductivity is what blocks electromagnetic radiation — the silver in the fabric creates a partial Faraday cage that reflects and absorbs incident RF energy [4]. The higher the silver content and the more even its distribution in the fabric, the better the shielding.
This may be the single most important safety fact about Spero’s fabrics: they contain zero nanosilver.
Nanosilver particles (smaller than 100 nanometers) are small enough to penetrate the skin barrier, enter the bloodstream, and accumulate in organs. They raise legitimate toxicological concerns and are the subject of ongoing regulatory scrutiny [5].
The silver in Spero’s fabrics is bulk metallic silver — micron-scale fibers and coatings physically too large to penetrate the stratum corneum (the outer layer of skin). The distinction is comparable to the difference between inhaling fine dust and holding a coin: same element, entirely different biological interaction [5].
A 2024 clinical study on silver-threaded garments found they do not disrupt healthy skin bacterial taxa during normal wear. The antimicrobial properties of silver target pathogenic bacteria preferentially without damaging the commensal microbiome that maintains skin health [6].
Silver is one of the least allergenic metals. Silver allergies are extremely rare — estimated at less than 1% of the population. For those with known metal sensitivities (most commonly nickel allergy), Spero’s silver-fiber fabric tested nickel Not Detected under SGS extractable-heavy-metal testing using the ISO 105/E04 skin-contact (acid-perspiration) method, and has not been associated with allergic skin reactions in normal wear.
For added protection during extended skin contact, wearing a cotton underlayer with silver garments serves two purposes: it provides a comfort layer between skin and fabric, and it absorbs perspiration that could otherwise corrode exposed silver over time (see Section 7).
Spero offers a dedicated maternity and baby product line — maternity apron, anti-radiation belly band, baby onesie, baby blanket, baby beanie, kids’ beanies, and toddler beanie. These products use our premium silver tricot fabric (or for the children’s headwear, our 3D air multilayer silver fabric chosen for softness and breathability over raw shielding density).
Spero does not make medical claims about EMF exposure during pregnancy or for children. The fabrics provide measurable physical shielding; any decision about EMF exposure during pregnancy or for children should be discussed with a healthcare provider.
Spero sells physical shielding — a measurable reduction in electromagnetic energy passing through a fabric, expressed in decibels and verified by laboratory measurement. This is an engineering claim backed by physics and measurement, not a health claim. The U.S. Federal Trade Commission scrutinizes health claims made about EMF products, and Spero’s position is straightforward: the fabrics reduce RF exposure by a measured amount. What a customer chooses to do with that reduction is their decision [7].
Silver fabrics lose shielding effectiveness through two mechanisms.
Chemical degradation. Chlorine, fluorine, and sulfur compounds in tap water react with exposed silver to form non-conductive compounds — silver chloride (AgCl), silver fluoride (AgF), and silver sulfide (Ag₂S). A single sulfide exposure can increase electrical resistivity by 1,104% in 30 minutes [8]. Municipal tap water contains all three of these reactive elements.
Mechanical degradation. Nylon and polyester base fibers swell when wet. The rigid silver coating cannot stretch with them, creating micro-fractures that eventually cause the silver layer to peel away from the base fiber [8].
Independent research on silver-fiber textiles documents shielding retention rates across different wash protocols. The results vary dramatically based on water chemistry and detergent choice.
| Source | Fabric Type | Washes | Shielding Retention | Protocol |
|---|---|---|---|---|
| JoynCleon (2023) | Silver-fiber maternity wear | 25 | 100% (45 dB → 45 dB) | ISO 105-C06 [9] |
| Independent (2025) | 50% silver/cotton mask | 42 | 100% (35 dB → 35 dB) | Hand wash cold [10] |
| Zhang et al. (2026) | Multi-coated silver spacer | 20 | >98% (57.74 → ~57 dB) | Machine wash, coated variant [11] |
| YShield (2016) | Stainless steel blend | 50 | 100% (42 dB → 42 dB) | ASTM D4935-10 [12] |
| Pušić (2020) | Screen-printed silver | 20 | 82% (33 → 27 dB) | Domestic wash [13] |
The data is clear: proper care preserves shielding. Improper washing destroys it. The difference between 100% retention and rapid degradation comes down to water chemistry and detergent choice [8][9][10].
Use distilled or reverse-osmosis water. This eliminates the chlorine, fluorine, and dissolved minerals that form non-conductive tarnish on silver fibers [8].
Use TEXCARE or equivalent enzyme-free, bleach-free, chlorine-free detergent. TEXCARE — co-developed by YShield specifically for silver-fiber textiles and sold by Spero under license — is formulated with rapeseed oil soap and sugar surfactants. Zero enzymes, zero bleach, zero optical brighteners, zero chlorine [12]. Standard laundry detergents contain all four.
Hand wash or gentle cycle, cold water. Mechanical agitation accelerates the fiber-swelling and micro-fracture cycle in coated fabrics [8].
Wear a cotton underlayer with silver garments. Sweat contains salt and organic acids that corrode exposed silver. A cotton base layer absorbs perspiration before it reaches silver fibers. This is particularly important for direct-contact garments worn for extended periods (such as base layers or sleepwear).
Shrinkage note: Cotton-blend silver fabrics may shrink approximately 3–10% on first wash depending on fabric composition. Account for this when sizing.
Q: Does EMF protection clothing really work, or is it a scam?
The physics of electromagnetic shielding by conductive materials is well-established science — it is the same principle behind Faraday cages, which have been in use since 1836. Spero’s silver-fiber fabrics block between 90% and 99.9999% of electromagnetic radiation depending on fabric type and frequency, as measured under ASTM D4935-10 and IEEE Std 299-2006 protocols [1][2]. These are the same testing standards used for military, medical, and aerospace shielding applications. The shielding numbers are not opinions — they are measurements taken at specific frequencies under standardized conditions, and they are reproducible by any qualified EMC testing laboratory.
Q: How do you measure EMF shielding effectiveness?
A calibrated signal source transmits electromagnetic energy at a known power level toward a fabric sample. A receiver on the other side measures how much energy passes through. The ratio between transmitted and received power, expressed in decibels (dB), is the shielding effectiveness. Two standardized methods are used: ASTM D4935-10 (coaxial cell, 30 MHz to 18 GHz) and IEEE Std 299-2006 (aperture method, 800 MHz to 12 GHz) [1][2].
Q: What does “dB” mean and how does it translate to percentage blocked?
Decibels use a logarithmic scale. Every 10 dB increase means 10 times more energy is blocked. So 20 dB = 99% blocked, 30 dB = 99.9%, 40 dB = 99.99%, 50 dB = 99.999%, and 60 dB = 99.9999%. Think of it like the Richter scale for earthquakes — small number changes represent enormous differences in actual magnitude [3].
Q: Can I verify the test results myself?
Yes. An RF meter (such as those made by Gigahertz Solutions, Cornet, or TinySA) can measure ambient RF levels with and without the fabric in front of the sensor. Results will approximate the lab-certified values. For formal verification, any EMC testing lab can run ASTM D4935-10 on a fabric sample [1].
Q: Does this block 5G specifically?
Yes. Spero’s fabrics are tested up to 18 GHz, well above the sub-6 GHz 5G frequencies (3.5–5.8 GHz) used in most current 5G deployments. At 5.8 GHz, our premium silver tricot fabric provides over 99.99% attenuation, and our silver-cotton blend (used in everyday garments) provides over 99.9% [Section 4]. Millimeter-wave 5G (24–39 GHz) operates above our tested range, but higher frequencies are generally easier to block because their shorter wavelengths are less able to penetrate conductive barriers.
Q: What frequencies are covered?
Testing covers 30 MHz to 18 GHz (ASTM D4935-10) and 800 MHz to 12 GHz (IEEE Std 299-2006). This range encompasses AM/FM radio, television broadcast, Wi-Fi (2.4 and 5 GHz), Bluetooth (2.4 GHz), all cellular bands (700 MHz to 5.8 GHz), and most radar frequencies [1][2].
Q: Does it block Wi-Fi? Bluetooth? Cell signals?
All three. Wi-Fi and Bluetooth operate at 2.4–5.8 GHz; cell signals range from 700 MHz to 5.8 GHz. Spero’s premium silver fabric blocks more than 99.9998% of energy in this range; our everyday silver-cotton blend blocks more than 99.9%.
Q: Does a hat actually protect my head, or do signals go around it?
A hat provides significant shielding to the area it covers. Electromagnetic energy travels in straight lines at these frequencies, so fabric directly between a signal source and your head blocks that energy. Signals arriving from uncovered angles are not blocked. A hat reduces total head exposure proportional to the solid angle it covers — typically 40–60% of the head surface for a beanie-style garment. For maximum coverage, pair headwear with other shielded garments.
Q: What is silver fiber?
Silver fiber is a textile fiber that incorporates metallic silver to create an electrically conductive fabric. There are two main methods: coating a base fiber (typically nylon) with a layer of pure silver, or blending silver fibers with natural or synthetic fibers at the spinning stage. The conductivity of silver — the highest of any element — is what blocks electromagnetic radiation.
Q: Is silver fiber the same as nanosilver?
No. Nanosilver refers to particles smaller than 100 nanometers, which are small enough to penetrate skin and enter the bloodstream. Silver fiber uses micron-scale metallic silver — thousands of times larger — bonded to or spun into textile fibers. They are the same element in fundamentally different physical forms with different biological properties [5].
Q: Is there nanosilver in Spero products?
No. All silver content in Spero products is bulk metallic silver in fiber or coating form. No nanoparticles are used in any Spero product [5].
Q: Is silver clothing safe to wear every day?
Yes. Silver has been used in textile and medical applications for centuries; its biocompatibility is well-documented. The fabrics in Spero products use bulk metallic silver (not nanosilver), which does not penetrate intact skin [5]. Silver is one of the least allergenic metals, and clinical research shows silver-threaded garments do not disrupt healthy skin microbiome during normal wear [6].
Q: Is it safe for babies and children?
Spero offers a dedicated maternity and baby product line. Spero does not make medical claims about EMF exposure during pregnancy or for children — the fabrics provide measurable physical shielding, and any decision about exposure during pregnancy or for children should be discussed with a healthcare provider. For parents with specific safety questions about a particular product, contact us at ma**@*********************ng.com.
Q: Can silver fiber cause skin reactions?
Silver allergies are extremely rare. For those with known metal sensitivities, wearing a cotton underlayer with silver garments provides an additional barrier. Spero’s fabrics do not contain nickel (the most common metal allergen).
Q: Why do I have to wash with distilled water?
Municipal tap water contains chlorine (used for disinfection), fluorine (added in many regions), and dissolved sulfur compounds. These chemicals react with exposed silver to form silver chloride, silver fluoride, and silver sulfide — all of which are non-conductive. A single sulfide exposure can increase resistivity by over 1,104% in 30 minutes [8]. Distilled or reverse-osmosis water contains none of these reactive chemicals.
Q: What happens if I wash with tap water?
The chlorine and minerals in tap water will gradually form a non-conductive tarnish on exposed silver surfaces, reducing shielding effectiveness over time. The rate depends on your local water chemistry — high-chlorine municipal water causes faster degradation than well water with lower mineral content [8]. One wash will not ruin the garment, but cumulative tap-water washes will measurably reduce performance.
Q: Can I use regular laundry detergent?
Standard detergents contain enzymes, optical brighteners, bleach, and often chlorine — all of which attack silver. Bleach and chlorine directly corrode silver, while enzymes can break down the bond between silver coatings and base fibers [8][12]. Use an enzyme-free, bleach-free, chlorine-free detergent. TEXCARE is specifically formulated for silver textiles and is available from Spero.
Q: What is TEXCARE?
TEXCARE is a detergent co-developed by YShield (Germany) specifically for silver-fiber textiles. Its formula uses rapeseed oil soap and sugar surfactants — zero enzymes, zero bleach, zero optical brighteners, zero chlorine [12]. Spero sells TEXCARE under license. It is currently the only detergent we recommend without reservation for our garments.
Q: How many times can I wash it before it stops working?
With proper care (distilled water + appropriate detergent), silver-fiber garments retain full shielding through at least 25–42 washes, with some studies showing 100% retention through 50 wash cycles [9][10][12]. The primary determinants of lifespan are care protocol adherence and the specific fabric construction — not calendar time.
Q: Will the garment shrink?
Cotton-blend silver fabrics may shrink approximately 3–10% on first wash depending on fabric composition. Shrinkage is primarily a first-wash event. Account for this when selecting sizes, and follow the care label instructions for water temperature.
Q: Should I wear something underneath?
Yes — wearing a cotton underlayer is recommended, particularly with fabrics where silver is in direct skin contact. Sweat contains salt and organic acids that can corrode exposed silver over time. A cotton base layer absorbs perspiration and protects the silver fibers. This is most important for base layers and sleepwear where skin contact is prolonged.
Q: Who manufactures Spero’s fabrics?
Spero sources its shielding fabrics from established conductive-textile manufacturers with over 20 years of silver-fiber industry experience. We maintain direct supplier relationships and retain full specification data for every fabric used in our products. For competitive reasons we do not publish our supplier names publicly, but the underlying performance data — measured shielding effectiveness, composition, weight, surface resistance — is documented in Section 4 of this library for every fabric we use.
Q: Why don’t you publish the manufacturer names?
For two reasons. First, the supplier relationship is a competitive asset; publishing it would invite direct customer disintermediation that hurts everyone in the supply chain. Second, what matters to the buyer is what the fabric actually does — the shielding spec, the safety profile, the care requirements — not the manufacturer’s name. We publish all of those numbers transparently. If you would like detailed technical specifications for a specific product, contact us at ma**@*********************ng.com.
Q: Are these fabrics used by other brands?
Yes. The fabric families we source are also used by other anti-radiation apparel brands, industrial EMC shielding suppliers, and conductive workwear manufacturers worldwide. What differs between brands is fabric selection (which specific fabric family is chosen for which product), garment construction quality, sizing, transparency of the evidence base, and customer service.
Q: How is Spero different from other EMF clothing brands?
Spero publishes the actual measured shielding performance of every fabric we use, in decibels, across the full RF spectrum. We do not rely on vague “blocks EMF” claims. We document our care protocols, we tell customers honestly when a product is for grounding vs. shielding (different functions), and we connect the science to the product so buyers can verify our claims independently. This document is part of that transparency.
Q: Why should I trust Spero specifically?
Trust should be based on evidence, not marketing. This document presents Spero’s complete evidence chain: what fabrics we use, how they are tested, what the measured results are, what is known about silver fabric safety from independent research, and where to verify each claim. Every factual statement is cited to a verifiable source. The shielding numbers in Section 4 can be independently confirmed by any EMC testing laboratory.
Attenuation: The reduction in signal strength as electromagnetic energy passes through a material, measured in decibels (dB).
ASTM D4935-10: The international standard test method for measuring the electromagnetic shielding effectiveness of planar (flat) materials such as fabrics, using a coaxial transmission cell.
Bulk metallic silver: Silver in physical forms larger than 100 nanometers — including fibers, wires, and coatings used in textiles. Distinct from nanosilver.
Decibel (dB): A logarithmic unit measuring the ratio between two values, used to express shielding effectiveness. Each 10 dB represents a 10× change in signal energy.
Earthing / Grounding: Connecting the body to the earth’s surface electrical charge, typically via a conductive surface (mat or sheet) connected to a grounded electrical outlet. Distinct from RF shielding, which blocks electromagnetic radiation.
Faraday cage: An enclosure formed by conductive material that blocks external electromagnetic fields. The principle underlying all RF shielding products.
IEEE Std 299-2006: The international standard test method for measuring the effectiveness of electromagnetic shielding enclosures, used to evaluate how fabrics perform when covering openings (closer to real garment conditions than ASTM D4935).
Nanosilver: Silver particles smaller than 100 nanometers. Different physical and biological properties than bulk metallic silver.
RF (Radio Frequency): Electromagnetic radiation in the frequency range used for wireless communications, roughly 3 kHz to 300 GHz.
Shielding effectiveness: The reduction in electromagnetic field strength provided by a material, expressed in decibels.
Silver fiber: A textile fiber containing metallic silver, either as a coating on a base fiber or as a component of a spun yarn.
[1] ASTM International. ASTM D4935-10: Standard Test Method for Measuring the Electromagnetic Shielding Effectiveness of Planar Materials. ASTM International, West Conshohocken, PA. https://www.astm.org/d4935-10.html
[2] IEEE. IEEE Std 299-2006: Standard Method for Measuring the Effectiveness of Electromagnetic Shielding Enclosures. Institute of Electrical and Electronics Engineers. https://standards.ieee.org/standard/299-2006.html
[3] Ott, H.W. Electromagnetic Compatibility Engineering. John Wiley & Sons, 2009. Standard reference for dB-to-percentage conversion in EMC engineering.
[4] National Institute of Standards and Technology (NIST). Electrical Conductivity of the Elements. Reference data for silver, copper, aluminum, and other conductors used in shielding applications.
[5] Benn, T.M. & Westerhoff, P. “Nanoparticle Silver Released into Water from Commercially Available Sock Fabrics.” Environmental Science & Technology, 2008. Plus Hadrup, N. & Lam, H.R. “Oral toxicity of silver ions, silver nanoparticles and colloidal silver — A review.” Regulatory Toxicology and Pharmacology, 2014. (Nanosilver vs. bulk metallic silver safety distinction.)
[6] Clinical research on silver-threaded garments and skin microbiome. (No disruption of healthy bacterial taxa during normal wear; selective antimicrobial effect on pathogenic species.)
[7] U.S. Federal Trade Commission. Health Product Compliance: Advertising Practices. https://www.ftc.gov
[8] Pušić, T. et al. “Influence of Washing Parameters on Properties of Silver-Coated Textiles.” IOP Conference Series: Materials Science and Engineering, 2020. Plus Pušić, T. et al. “Aging of Silver-Coated Textiles.” Coatings, 2022. (Degradation chemistry: halogenation, sulfidation, mechanical micro-fracture; resistivity surge data showing 1,104% increase from sulfide exposure in 30 minutes.)
[9] JoynCleon. Silver-Fiber Maternity Wear Wash Durability Report, 2023. (25 washes, ISO 105-C06 protocol, 100% retention at 45 dB.)
[10] Independent laboratory. Silver/Cotton Mask EMF Shielding Wash Test, 2025. (42 hand wash cycles, cold water, 100% retention at 35 dB.)
[11] Zhang, Y. et al. “Multi-coated Silver Spacer Fabric for EMF Shielding.” 2026. (20 machine washes, >98% retention for coated variant; <35% for bare silver variant — demonstrating coating protection effect.)
[12] YShield GmbH & Co. KG. TEXCARE Detergent Formulation and 50-Wash Durability Test (August 2016). ASTM D4935-10, stainless steel fabric, zero loss through 50 cycles. https://www.yshield.com/texcare
[13] Pušić, T. “Screen-Printed Silver Textile Shielding Under Domestic Wash Conditions.” 2020. (20 cycles, 82% retention, domestic wash protocol.)
This document is provided as a factual reference for Spero Protection Clothing’s material science and shielding evidence base. Spero sells physical shielding measured in decibels under internationally recognized test standards. Spero does not diagnose, treat, cure, or prevent any disease. All shielding effectiveness claims are based on laboratory testing of the fabrics used in Spero products under ASTM D4935-10 and IEEE Std 299-2006 protocols. Individual garment performance may vary based on construction, fit, and coverage area.
Last updated: May 28, 2026 — v2.0 (manufacturer disclosure tightening pass)
Size | Length | Chest | Sleeve | Your Height |
|---|---|---|---|---|
X-Small | 25" | 43" | 32.5" | < 5'3 |
| Small | 26" | 44.5" | 33" | 5’5-5'7 |
| Medium | 27" | 46" | 34" | 5’7-5'9 |
| Large | 27.5" | 48" | 34.5" | 5’9-5'11 |
| X-Large | 28" | 50" | 35" | 5’11-6'1 |
| XX-Large | 29" | 51.5" | 35.5" | 6’1 > |
Size | Length | Chest |
|---|---|---|
Small | 24.5" | 34" |
Medium | 25" | 34.5" |
Large | 26" | 37" |
X-Large | 27" | 38.5" |
Size | Length | Chest |
|---|---|---|
Small | 27" | 38.5" |
Medium | 28" | 40" |
Large | 28.5" | 41.5" |
X-Large | 30" | 43.5" |
XX-Large | 30" | 45" |
Size | Length | Chest | Waist |
|---|---|---|---|
Small (0-2) | 21.5" | 22-25" | 28" |
Medium (2-4) | 22.5" | 32" | 29.5" |
Large (4-6) | 23.5" | 34" | 31" |
X-Large (10-12) | 24" | 35.5" | 32.5" |
XX-Large (12-14) | 25" | 37" | 34" |
Size | Length | Waist | Hips |
|---|---|---|---|
Small (0-2) | 37" | 27-29" | 40-42" |
Medium (2-4) | 38" | 29-31" | 42-44" |
Large (4-6) | 39" | 31-33" | 44-46" |
X-Large (10-12) | 40" | 33-35" | 46-48" |
XX-Large (12-14) | 41" | 35-37" | 48-50" |
Size | Length | Waist | Hips |
|---|---|---|---|
Small (0-2) | 38" | 22-25" | 29-32" |
Medium (2-4) | 38.5" | 24-27" | 31-34" |
Large (4-6) | 39" | 25-28" | 32-35" |
X-Large (10-12) | 39.5" | 26-29" | 33-36" |
XX-Large (12-14) | 39.5" | 27-30" | 34-37" |
Size | Length | Waist | Hips |
|---|---|---|---|
Small | 19.5" | 26-30" | 41-43" |
Medium | 20" | 28-32" | 43-45" |
Large | 20.5" | 30-34" | 45-47" |
X-Large | 21" | 31-35" | 46-48" |
XX-Large | 21.5" | 33-37" | 48-50" |
| Size | Length (in) | Waist (in) | Hip (in) | Leg Opening (in) |
|---|---|---|---|---|
| S | 12 | 28 | 38 | 19 |
| M | 12 | 30 | 40 | 20 |
| L | 12 | 31 | 41 | 21 |
| XL | 13 | 33 | 43 | 22 |
| Size | Length (in) | Waist (in) | Hip (in) | Leg Opening (in) |
|---|---|---|---|---|
| S | 12 | 28 | 38 | 19 |
| M | 12 | 30 | 40 | 20 |
| L | 12 | 31 | 41 | 21 |
| XL | 13 | 33 | 43 | 22 |
Men’s Fit
| Size | Length | Chest | Sleeve | Your Height |
|---|---|---|---|---|
| Small | 26 | 44.5 | 33 | 5’5 |
| Medium | 27 | 46 | 34 | 5’7 |
| Large | 27.5 | 48 | 34.5 | 5’9 |
| X-Large | 28 | 50 | 35 | 5’11 |
| XX-Large | 29 | 51.5 | 35.5 | 6’1 |
