The scale · XRS 001:2026, Clauses 7 to 10
Six levels, one quantity, four readings.
Everything on this page is reproduced from the reference document: the input quantity, Table 7 in full, the origin of each boundary, the four use profiles and the shape factor. The calculator applies the same rules to your own bench measurement.
- XRS 001:2026
- First edition
- 2026-08
- CC BY-ND 4.0
XRS 001:2026 is a proprietary technical reference published under the sole responsibility of XALPES LLC. It is not a standard, has no regulatory value, does not classify filtration efficiency and does not authorize any regulated use. Human-panel validation (clause 14) has not yet been conducted.
The quantity
One input: specific resistance.
A pressure drop in pascals means nothing on its own: it depends on the flow at which it was measured. The XRS scale is built on the pressure drop divided by the flow that produced it.
Rs = Δp / Q
- Δp
- pressure drop across the mask, in pascals (Pa)
- Q
- test flow, in litres per second (L/s)
- Rs
- specific resistance, in Pa/(L·s⁻¹) — the only input of the scale
- Flow invariance verified to better than ± 11 % on the normative values (Table 3 of the reference)
- Declared uncertainty band: ± 12 % on Rs
- A measurement within 12 % of a boundary is recorded as lying in the overlap band; the least favourable level is attributed
- A device carries one level only — never a pair, an interval or an "in-service" level
The scale
Six levels, X1 to X6.
Table 7 of XRS 001:2026, reproduced in full. The capitalized wording that opens each breathing-endurance cell is the normative short form, taken up word for word by any marking.
| Level | Rs Pa/(L·s⁻¹) | Comfort qualification | Breathing endurance |
|---|---|---|---|
| X1 | ≤ 30 | Neutral comfort — resistance not perceptible | NO LIMIT — Continuous wear without time limit, including for sensitive groups (children, elderly people, people with reduced respiratory capacity) and during sleep. |
| X2 | 30 – 60 | High comfort — at the limit of perception | ALL DAY — Continuous wear over a full day without imposed breaks: office, school, retail, transport, urban travel. |
| X3 | 60 – 100 | Ordinary comfort — perceptible, without discomfort | SEVERAL HOURS — Wear of several hours interspersed with natural breaks: active standing work, light handling, brisk walking. |
| X4 | 100 – 140 | Degraded comfort — distinct breathing effort | 1 TO 2 HOURS — Wear in sequences of one to two hours, followed by a recovery break. Reserved for healthy adults. |
| X5 | 140 – 200 | Constrained comfort — established breathing discomfort | UNDER 1 HOUR — Wear in short sequences, under one hour, with mandatory breaks. Trained subject, supervised task. |
| X6 | > 200 | Critical comfort — major breathing constraint | 20 TO 30 MINUTES — Brief, exceptional wear, in the order of twenty to thirty minutes. Verified medical fitness and supervision required. Unsuitable for prolonged wear and for sensitive groups. |
Note 1 — Comfort and filtration are two independent dimensions: the breathing-endurance column carries no reference to a protection class. A mask can be X2 and highly filtering, or X5 and poorly filtering.
Note 2 — The capitalized short forms are taken up word for word, without paraphrase, rounding or conversion, by any document or marking stating an XRS level, always under the heading "breathing endurance". The level applies to a new mask, within the conditions of use set by the manufacturer.
French text is authoritative; this translation is provided for information. See XRS 001:2026(F).
Origin of each boundary
No threshold is set by convention.
Table 8 of the reference, condensed. Each boundary refers to a measured or published external reference.
- X1 / X230Half of the detection floor. Safety margin for groups whose perception threshold is lowered: children, elderly people, reduced respiratory capacity.
- X2 / X360Floor of the measured detection threshold (58.8 Pa/(L·s⁻¹)), rounded conservatively. Boundary between the imperceptible and the perceptible — the best-supported boundary of the scale.
- X3 / X4100Exit of the detection band (74.5 Pa/(L·s⁻¹)) plus the uncertainty margin, and vicinity of the most demanding published breathability ceiling (103.8 Pa/(L·s⁻¹)). Beyond, resistance is no longer merely perceived: it is endured.
- X4 / X5140Resistance ceiling admitted for the most widespread intermediate filtration class. A mask at this level is at the upper limit of what references tolerate in everyday use.
- X5 / X6200Ceiling of the highest filtration class. Independently confirmed by the standardized physiological limits: Rs ≤ 218 by peak pressure and Rs ≤ 208 by work of breathing at the highest sustained work rate (clause 13).
- Beyond X6242Most permissive absolute approval ceiling on record. Serves as a safety bound: beyond it, no use is conceivable.
Four use profiles
One scale, four readings.
Since Rs does not depend on flow, one scale generates four application tables. A mask keeps its level whatever the profile; only the measured Δp and the work of breathing change, because they describe what the wearer actually experiences in that situation.
| Profile | Bench flow | Equivalent minute ventilation | Physiological situation |
|---|---|---|---|
| P1 | 30 L/min | ≈ 10 L/min | Rest, seated position |
| P2 | 60 L/min | ≈ 19 L/min | Light to moderate activity |
| P3 | 95 L/min | ≈ 30 L/min | Sustained occupational effort |
| P4 | 140 L/min | ≈ 45 L/min | Intense, athletic effort |
Table 9 — Profile P1, rest / sedentary
Test flow 30 L/min · equivalent minute ventilation ≈ 10 L/min| Level | Rs Pa/(L·s⁻¹) | Measured Δp (Pa) | WoB/VT (J/L) | Comfort qualification |
|---|---|---|---|---|
| X1 | ≤ 30 | 0 – 15 | 0.00 – 0.02 | Neutral comfort — resistance not perceptible |
| X2 | 30 – 60 | 15 – 30 | 0.02 – 0.05 | High comfort — at the limit of perception |
| X3 | 60 – 100 | 30 – 50 | 0.05 – 0.08 | Ordinary comfort — perceptible, without discomfort |
| X4 | 100 – 140 | 50 – 70 | 0.08 – 0.11 | Degraded comfort — distinct breathing effort |
| X5 | 140 – 200 | 70 – 100 | 0.11 – 0.16 | Constrained comfort — established breathing discomfort |
| X6 | > 200 | > 100 | > 0.16 | Critical comfort — major breathing constraint |
Table 10 — Profile P2, moderate activity
Test flow 60 L/min · equivalent minute ventilation ≈ 19 L/min| Level | Rs Pa/(L·s⁻¹) | Measured Δp (Pa) | WoB/VT (J/L) | Comfort qualification |
|---|---|---|---|---|
| X1 | ≤ 30 | 0 – 30 | 0.00 – 0.05 | Neutral comfort — resistance not perceptible |
| X2 | 30 – 60 | 30 – 60 | 0.05 – 0.09 | High comfort — at the limit of perception |
| X3 | 60 – 100 | 60 – 100 | 0.09 – 0.16 | Ordinary comfort — perceptible, without discomfort |
| X4 | 100 – 140 | 100 – 140 | 0.16 – 0.22 | Degraded comfort — distinct breathing effort |
| X5 | 140 – 200 | 140 – 200 | 0.22 – 0.31 | Constrained comfort — established breathing discomfort |
| X6 | > 200 | > 200 | > 0.31 | Critical comfort — major breathing constraint |
Table 11 — Profile P3, sustained effort
Test flow 95 L/min · equivalent minute ventilation ≈ 30 L/min| Level | Rs Pa/(L·s⁻¹) | Measured Δp (Pa) | WoB/VT (J/L) | Comfort qualification |
|---|---|---|---|---|
| X1 | ≤ 30 | 0 – 48 | 0.00 – 0.07 | Neutral comfort — resistance not perceptible |
| X2 | 30 – 60 | 48 – 95 | 0.07 – 0.15 | High comfort — at the limit of perception |
| X3 | 60 – 100 | 95 – 158 | 0.15 – 0.25 | Ordinary comfort — perceptible, without discomfort |
| X4 | 100 – 140 | 158 – 222 | 0.25 – 0.35 | Degraded comfort — distinct breathing effort |
| X5 | 140 – 200 | 222 – 317 | 0.35 – 0.50 | Constrained comfort — established breathing discomfort |
| X6 | > 200 | > 317 | > 0.50 | Critical comfort — major breathing constraint |
Table 12 — Profile P4, maximal / athletic effort
Test flow 140 L/min · equivalent minute ventilation ≈ 45 L/min| Level | Rs Pa/(L·s⁻¹) | Measured Δp (Pa) | WoB/VT (J/L) | Comfort qualification |
|---|---|---|---|---|
| X1 | ≤ 30 | 0 – 70 | 0.00 – 0.11 | Neutral comfort — resistance not perceptible |
| X2 | 30 – 60 | 70 – 140 | 0.11 – 0.22 | High comfort — at the limit of perception |
| X3 | 60 – 100 | 140 – 233 | 0.22 – 0.37 | Ordinary comfort — perceptible, without discomfort |
| X4 | 100 – 140 | 233 – 327 | 0.37 – 0.51 | Degraded comfort — distinct breathing effort |
| X5 | 140 – 200 | 327 – 467 | 0.51 – 0.73 | Constrained comfort — established breathing discomfort |
| X6 | > 200 | > 467 | > 0.73 | Critical comfort — major breathing constraint |
Note — The same mask keeps its XRS level whatever the profile, since Rs is invariant. The Δp and WoB/VT columns change from one table to the next because they describe what the wearer actually experiences in the situation considered. WoB/VT values are analytical estimates (clause 11), not measurements.
French text is authoritative; this translation is provided for information. See XRS 001:2026(F).
Calculator
From a bench measurement to a level.
Design aid only — a level may only be declared under the conditions of XRS 002 and with XALPES LLC's written authorization. Nothing is stored or transmitted.
Enter a pressure drop and a test flow. The specific resistance Rs = Δp / Q is computed with Q converted to litres per second.
New mask · within the conditions of use set by the manufacturer. Human-panel validation not yet conducted.
Geometry & form factor
Surface is a stronger lever than media.
What crosses the filtration media is not a flow but a velocity. Two masks cut from the same media can show resistances in a ratio of one to three from geometry alone.
u = Q / A
- u
- face velocity through the media, cm/s
- A
- useful filtering surface, cm²
φ = A_ref / A
- A_ref
- 236 cm², reference duckbill surface measured in the literature
- φ
- form factor; Rs ≈ φ × Rs_reference — φ > 1 degrades breathability, φ < 1 improves it
| Geometry | Surface A | Factor φ | Status of the value |
|---|---|---|---|
| Flat three-fold | ≈ 150 cm² | 1.57 | XALPES estimate, to be confirmed by measurement |
| Rigid moulded cup | ≈ 180 cm² | 1.31 | XALPES estimate, to be confirmed by measurement |
| Duckbill | 236 cm² | 1.00 | Published measured value — reference of the scale |
| Fish type / folded boat | ≈ 300 cm² | 0.79 | XALPES estimate, to be confirmed by measurement |
| Large-surface pleated | 415 cm² | 0.57 | Published measured value |
To target a high XRS level under effort, increasing the developed surface is a more powerful lever than the choice of media. The three estimates are the first task of the measurement program (clause 14.2).
French text is authoritative; this translation is provided for information. See XRS 001:2026(F).
Level pages
What each level means for the wearer.
Each level has a technical sheet: the endurance, the qualification, the origin of the boundary and what the level does not say. The code on the pack leads to a shorter page of the same level, written for the wearer.