CAR · L1 · Scent plaque · citrus-dry
A 32 g plaque clipped to a vent in a cabin that swings 22 C
A parked car reaches 55-70 C in summer and drops below freezing in winter, and a 3.2 m2 cabin fully encloses whatever you put in it. A 32 g plaster plaque at only 9% load, on a clip rather than loose in the cabin, survives both extremes and holds an L1 read for 41 days at CNY 12 a month.
By The Scent Desk·Published 2026-10-23
- One fill lasts 41 d
- Coverage 2.5 m2
- Refill cycle 41 d
- Running cost CNY 12
Dot spacing and radius are driven by the rung, the field width by the covered area, and the second field by the room's air class. Both fields are generated at build time from the room and carrier records.
| Floor area | 3.2 m2 |
|---|---|
| Air exchange | draughty |
| Household | no pets or small children |
| Direction | citrus-dry |
| Carrier | Scent plaque PLQ |
Refill calculator
Change the area or the air class and the server recomputes the cycle. The script upgrades this to a live preview; with the script off the button still works.
Basis: 3.2 m2 · draughty. A smaller floor area, so the unit count can come down — but the refill interval does not stretch linearly, because a small room saturates sooner. Air class unchanged from the original plan.
The first rule in a car is subtract before you add
A 3.2 m2 cabin at 1.25 m holds about 4 m3, among the smallest volumes in the register, and it has to survive a 22 C swing across the year. Plastics, leather and seat foam all release their own volatiles as the cabin heats, and those compounds are what "car smell" actually is. Fragrance goes on top of all of it, which is why the dose starts at half the household figure rather than at parity.
The working rule is: take the room you would specify at home, and drop it one rung. A household L2 set-up in a cabin produces a close, heavy feeling on the first drive that does not lift as the journey continues, because a cabin does not exchange its air.
Nine percent load on a 7 mm body
Cabin temperatures rule out anything that softens. Wax tablets and any paste-consistency carrier will slump in a 60 C interior, which is the first reason a plaque wins here. Plaster and compressed fibre both hold their shape to well past 70 C.
A 9% load on a 7 mm body carries about 1.1 ml of oil. That sounds like very little, and in an almost sealed 4 m3 space with a 41-day life it is the right order of magnitude. Above 12% the first two days in summer sun read noticeably sharp, and the plaque spends the rest of its life at a lower steady state than a correctly loaded one.
Mounting: on a vent, never lying flat
Lying flat on the dash or under a seat is the commonest mistake. Flat, the underside cannot release at all, the plaque slides under braking, and in summer it leaves a print on whatever it rested on. A vent clip does three jobs at once — it fixes the plaque, it keeps air under it, and it hands you a control via the blower.
Use a centre vent rather than a side vent under a window. If a side vent is the only option, angle the louvres away from the plaque rather than letting them blow straight onto it, which drives output up sharply on every journey.
How the seasons change the plan
- Summer, above 30 C. Output runs about 1.5 times nominal and the life shortens to roughly 28 days. Turn the plaque so the vent only reaches its edge.
- Winter, below 10 C. Output falls to 40-50% of nominal and the read is very faint. This is expected — do not replace the plaque on the strength of it, because a fresh one will overshoot badly the moment spring arrives.
- Wet season. Plaster takes on moisture and lifts its output slightly. If a damp note appears, take the plaque indoors for a day and re-fit it.
Cost: CNY 12 a month
A 32 g plaster plaque costs about CNY 12 and lasts 41 days, which is CNY 9 a month. A vent bracket is a one-off CNY 8 and lasts indefinitely. Summer acceleration takes the real usage to about 1.2 plaques a season, and the measured figure lands at CNY 12 a month.
Diagnosis
- Heavy and close on the first drive. The dose was set at household strength. Drop to a 9% load, or move the plaque out of the direct vent path.
- Nothing at all in winter. Expected. Do not fit a new plaque; re-assess when the temperature comes back up.
- The plaque has warped or left a print. It was lying flat on the dash. It has to be on a clip.
- A plastic note in the scent. The plaque was against a soft-touch dash and picked up plasticiser at high temperature. Move it, and air it indoors for a day.
- It rattles. The bracket is loose. A rattle is a safety item in a car, not an annoyance — re-seat or remove the clip.
Assembly, in order
- Choose the face material — Plaster and fibre board differ in exactly one way that matters: plaster pulls moisture out of the air and releases it again, fibre board does not. In a bathroom or a kitchen, take the board.
- Load the face, not the body — Brush two to three millilitres onto the unglazed face with a pipette and leave it face up for twelve hours. Loading the edges wastes oil into the air you are standing in.
- Hang it clear of fabric — Hang the plaque at least fifteen centimetres from any textile. Closer than that and the fabric becomes the second reservoir, and the room reads as one flat note.
- Wipe before you re-oil — Wipe the face with a dry cloth before the second load. Old oil that has oxidised on the surface stops the new load from migrating out.
Code PLQ · the whole body of the plaque is the reservoir; scent migrates to the surface and evaporates
What it costs to keep running
| Running cost | CNY 12 |
|---|---|
| One fill lasts | 41 d |
| Refill cycle | 41 d |
| Coverage | 2.5 m2 |
| Refill and replacement | 32 g plaster plaque, 7 mm thick, vent clip bracket |
Failure diagnosis for L1
| What you notice | What caused it | What to change |
|---|---|---|
| Nothing at all, even with your head inside the wardrobe | The filler has gone flat, or the pouch is lying flat against the wood and half its surface is doing nothing | Squeeze or re-oil the filler and stand the pouch side-on. A flat pouch in a sealed volume loses about a third of its output. |
| It reads while you are still in the doorway | Too many units for a 1-5 m2 volume. Two carriers in one wardrobe is the usual version of this. | Take one unit out and leave the door open for an hour. Judge again the next day, not the same evening. |
| A sharp patch right beside the carrier | Neat oil has landed on the filler, or something is being held within the near field | Replace the filler. Nothing dilutes in place, and moving an L1 carrier into an open room does not fix a concentration problem. |
Same room, other rung
Nothing at this rung has come off the drip yet.
Open the rung card — L1 · Barely there
This record went live on 2026-10-23. Records dated later in the register are not listed anywhere on the site until their date arrives.