D and G: Particulate Testing

This chapter defines the scale, dose, procedure and grading shared by the D (dust) and G (grit) groups. The two groups differ only in their test medium and full dose, which are defined in their own chapters.

Exposure area

A = sum of (length × width) of the largest face of each rigid section, in cm²

Note (informative): Dose scales with exposure area, not mass. Particles get in through surfaces, seams and moving parts, so a dense device and a light device of the same size have the same exposure. Devices with hinges receive a larger dose automatically, in proportion to their extra surfaces and seams.

Dose

Dose (g) = (A ÷ 100) × F × p

1. Every dose shall be weighed. The weighed mass is the dose.
2. Volume measures may be used as rough guidance only (see Volume Conversions).

Note (informative): Powders pack differently depending on the product and how they are scooped. One tablespoon (15 mL) of dry sand weighs roughly 23 g, but a tablespoon of fine powder can weigh anywhere from about 5 to 15 g. This is why doses are weighed rather than measured by volume.

Example doses (informative)

Scale

Levels are cumulative: each level adds more medium and more cycles on top of the previous level, with no cleaning in between.

For each level, the dose increment shall be the difference between that level’s cumulative dose and the previous level’s, and the cycles run shall be the difference between their cumulative cycles.

Note (informative): Cumulative levels reproduce debris building up over time.

Cycle

One cycle means operating every moving part through its full range once, at about one cycle every 2 seconds:

Procedure

Procedure steps are written in the imperative and are requirements unless they say otherwise. Equipment is listed in Kits and safety requirements in Safety.

Before testing

1. Confirm the unit meets Test Conditions, including its baseline for this group.
2. Measure the exposure area and calculate the dose for every level.
3. Home tier: the tester may choose a maximum level in advance.

Each level

1. Weigh the dose increment for this level.
2. Place the unit on the raised rack inside the bin, in its most open state (hinged devices fully open; slab devices front face up). The rack shall hold the unit clear of medium that has fallen to the bin floor.
3. Apply half the increment, sprinkled evenly from about 10 cm above. The medium may be shaken through the #20 sieve to give an even spread.
4. Brush each seam, hinge line and port opening with 5 light strokes.
5. Run half the level’s cycles.
6. Turn the unit over on the rack (hinged devices: close it). Apply the other half of the increment to the exposed faces, edges and ports, brush, and run the remaining cycles.
7. Shed loose material: hold the unit edge-down and tap it 3 times on each long edge onto a folded towel. Do not blow or wipe the seams at this stage.
8. Measure every applicable effect (see Measurements) and record the results.
9. Grade the level (see Grading) and decide whether to continue (see Stop rules).

Note (informative): Without the rack, a unit turned over in step 6 would lie in the medium that fell during the first half, so its real dose would depend on the size of the bin.

Stop rules

Note (informative): Home testers stop at the first sign of degradation to give the device the best chance of surviving.

After testing

Grading

1. A level is passed if no uppercase effect appeared after it.
2. The digit is the highest level passed (0 if level 1 failed).
3. Effect letters and the failure letter shall be written per Code Format, including the failure-letter priority order and the meaning of an absent failure letter.
4. Enclosure breaches found at teardown are handled per Test Tiers.

Examples (hypothetical)