Airflow reality checks in potato storages: Finding dead zones before rot finds them

Potato storage problems rarely begin as dramatic events. More often, they begin as uneven airflow – a quiet shift that creates pockets of warmer tubers, higher respiration, localized moisture movement, and ultimately the conditions where breakdown accelerates.

This is the fourth article in Potato News Today’s Storage Season Essentials series, following three earlier installments published in late January 2026. Like the previous articles, this one is built for the people who carry the responsibility of the pile – one practical baseline at a time.

Early in the season, some facilities can “get away with” imperfect airflow because the system is still transitioning. By late winter, that margin narrows. If air is short-circuiting, if a plenum is unbalanced, if one wall zone is starved, or if resistance has changed across part of the pile, dead zones form – and dead zones are where rot risk tends to concentrate.

What follows is a practical storage-floor playbook for identifying airflow trouble before it becomes a late-season quality story.

Why airflow is the hidden backbone of storage performance

Airflow is not simply “moving air.” In potato storage, airflow is the delivery system for:

• temperature control and temperature uniformity across the pile
• moisture management (reducing condensation risk and preventing over-drying)
• gas management (removing CO₂ and avoiding stale pockets)
• keeping the pile predictable so small issues stay small

When airflow is even, everything else becomes easier: temperature gradients tighten, CO₂ stays more uniform, warm zones don’t persist, and moisture is less likely to migrate into trouble spots. When airflow is uneven, the storage becomes a patchwork of microclimates – and microclimates are where late-season surprises are born.

What a “dead zone” looks like in real life

A dead zone is a part of the pile where air exchange is insufficient compared to the rest of the storage. It does not always mean “no airflow.” It often means “not enough airflow for what the biology is doing there.”

Common signatures include:

• a persistent warm spot that does not respond to normal fan cycles
• CO₂ drifting upward in one area (where CO₂ is measured)
• recurring issues in the same corner, same wall line, or same bay each year
• condensation evidence or damp odours that appear locally after warm spells
• a zone that cools or equalizes much slower than neighboring zones

In many storages, dead zones are less about one catastrophic failure and more about small imbalances – a leak here, an obstruction there, a distribution change caused by compaction, frost, or a shifted pile profile.

Why dead zones become rot zones

Rot risk in storage is rarely “random.” It tends to follow physics and biology:

• warm tubers respire more, generating additional heat and moisture
• respiration produces CO₂, and stale air lingers where exchange is weak
• moisture migrates and condenses where temperature and airflow conditions allow it
• localized wetness plus warmth plus limited air exchange creates ideal breakdown conditions

Dead zones also amplify the damage of short weather events. A warm spell may be brief, but if it triggers condensation in a weak-airflow pocket, that pocket can stay biologically active long after outside air returns to “normal.”

The airflow reality check mindset

A practical way to approach airflow is to stop asking, “Are the fans running?” and start asking:

• Is the pile responding evenly?
• Is the air going where we think it’s going?
• Are there signs of short-circuiting or bypass?
• Has resistance changed in parts of the pile?

That mindset changes your checks from routine to diagnostic.

Short-circuiting: the quiet thief of airflow

Short-circuiting occurs when air takes the path of least resistance instead of moving through the pile as intended.

Common causes:

• leaks at doors, joints, louvers, or duct connections
• poorly sealed plenums
• bypass pathways created by building pressure differences
• uneven pile depth or voids
• distribution layouts that unintentionally favor one zone

What it looks like operationally:

• the storage “seems ventilated,” but some pile zones barely respond
• fans run longer with diminishing effect
• CO₂ improves in one area but stays elevated in another (if measured)
• warm corners persist even when most of the building appears stable

In short: you can run fans for hours and still starve parts of the pile if air is not being forced through tubers uniformly.

Resistance changes: airflow can weaken mid-season even with the same equipment

Even if nothing “breaks,” resistance through the pile can change as the season progresses:

• compaction in parts of the pile
• localized frost/ice effects in intake/exhaust areas or ducting
• blocked perforations or restricted pathways
• changes in pile porosity due to soil, clods, or variability in tuber size distribution

This is why a storage that looked uniform earlier can start drifting later. The system may be the same, but the airflow pathways – and resistance – are not.

The measurements that expose airflow problems fastest

You do not need perfect instrumentation. You need a few consistent signals.

Most useful signals include:

• pile temperature patterns (not just averages)
• supply air and plenum temperatures (what you actually deliver)
• static pressure trends (where available)
• CO₂ trend and zone comparisons (where measured)
• walk-through indicators: fogging at openings, damp odours, frost pattern shifts, localized wetness

The key is comparing zones and looking for repeat patterns that don’t self-correct.

A practical airflow audit: what to do weekly in late winter

This routine is intentionally written to work in both low-tech and high-tech facilities.

Step 1: Identify the least responsive zone

• use your temperature map or consistent probe points
• find the area that equalizes slowest after typical fan cycles
• note whether it is a repeat offender

Step 2: Verify supply and plenum delivery

• confirm supply air temperature delivered to the plenum
• if the plenum runs long distances, check more than one point if possible
• look for suspicious differences that suggest uneven distribution

Step 3: Look for bypass and short-circuiting clues

• doors and seals: evidence of unintended air movement
• louvers and joints: leaks, unusual frost patterns, dampness
• wall lines and corners: recurring dampness or stable warm zones

Step 4: Use pressure and CO₂ if available

• static pressure drifting upward can indicate rising resistance or blockage
• CO₂ rising in one zone more than others often signals insufficient exchange

Step 5: Confirm with a walk-through and sensory checks

• localized odour changes matter
• new condensation evidence matters
• changing frost/drip patterns matter

Step 6: Document and set a re-check trigger

• what you saw, what you think it means, what you changed
• schedule a follow-up check (specific day/time)

Common dead zone root causes and what to check first

If a zone is behaving differently, these are frequent causes.

Leaks and bypass routes

• doors, seals, transitions, pressure-sensitive points
• unusual frost or dampness that tracks air leakage

Distribution imbalance in the plenum

• temperature differences along the plenum
• partial blockages or restrictions feeding the weak zone

Pile geometry and loading effects

• uneven pile depth biases airflow strongly
• voids can create easy pathways that bypass denser areas
• soil-heavy or clod-heavy sections increase resistance locally

Warm-spell aftermath

• brief condensation events can create localized wetness
• wetness plus weak exchange can accelerate biological activity

What not to do when you suspect a dead zone

These moves look like action but often increase risk:

• running long fan cycles everywhere “just to be safe”
• changing multiple setpoints at once without documenting why
• chasing one sensor without validating with physical inspection
• ignoring a small recurring warm zone because “the average looks fine”

The goal is targeted diagnosis and targeted response, not whole-building overcorrection.

Common airflow myths that lead to bad decisions

This is where many storages lose control without realizing it – not because people don’t care, but because a few “sounds right” ideas get repeated.

Myth 1: If the fans are running, airflow must be fine.
Reality: fans can run for hours while air short-circuits and bypasses key zones. Fan run time is not proof of even distribution.

Myth 2: Average pile temperature tells the story.
Reality: averages hide risk. A storage can show a comfortable average while one corner quietly warms, produces moisture, and becomes biologically active.

Myth 3: Longer fan runs always fix uneven zones.
Reality: longer runs can worsen dehydration or import moisture during risk windows – while still failing to move air through a dead zone.

Myth 4: Dead zones are rare and only happen in “bad buildings.”
Reality: dead zones are common, especially in late winter, because resistance changes over time and small leaks or obstructions become meaningful.

Myth 5: Condensation is only a “warm spell problem,” not an airflow problem.
Reality: condensation risk and airflow weakness often work together. Moisture events do their worst damage in weak-exchange pockets.

One-page Airflow Reality Check table

Airflow check	What to look for	Normal	Watch	Act now	Notes / actions
Least responsive zone	Which area equalizes slowest after typical fan cycles?	Zones respond similarly	One zone lags repeatedly	Persistent warm spot / non-response
Pile temperature pattern	Top/mid/bottom and centre/perimeter differences	Stable or narrowing gradients	Gradients widening slowly	Fast widening or localized warming
Supply air and plenum	Delivered air temperature and consistency along plenum	Consistent delivery	Uneven plenum temps	Clear distribution imbalance
Short-circuiting clues	Leaks, bypass routes, odd frost/damp patterns near doors/louvers/joints	No unusual patterns	Minor recurring signs	Strong evidence of bypass
Static pressure (if available)	Weekly trend at consistent points	Stable	Slow upward drift	Rapid drift or big differences
CO₂ trend (if available)	Compare zones and track direction over weeks	Stable and uniform	Creeping or uneven	Rising in one zone + warm spot + odour
Walk-through confirmation	Odour, condensation evidence, frost/drip shifts, top-of-pile dampness near walls	No new signs	Minor localized changes	Repeated moisture/odour in one area
Documentation	What changed, what it means, what was adjusted, re-check time set	Clear weekly notes	Partial notes	No rationale / no follow-up plan

Takeaway

Dead zones are not a mystery problem – they are usually a pattern problem. They announce themselves through uneven temperature response, localized moisture signals, and zone differences that repeat week after week. The earlier you recognize those patterns, the more calmly you can respond: verify supply delivery, look for bypass routes, check for changing resistance, and increase monitoring in exactly the place where the storage is losing uniformity.

In late winter, the best storage managers are not the ones who “do the most.” They are the ones who notice drift early, diagnose it precisely, and make small, targeted corrections before rot organisms ever get their preferred conditions.

Author: Lukie Pieterse, Editor/Publisher Potato News Today