Every January, we hear a version of the same question from members: their swab results came back different this month, and nothing in the make room changed. Usually something did change — just not in the make room. Winter heating runs dry the air moving through a facility, and an aging room that held steady at 85% relative humidity in October can drift lower once the furnace kicks on next door, even with the cave's own humidifier working normally. A drier room changes the surface conditions bacteria are growing in, which is exactly the kind of shift a seasonal swab plan is supposed to catch before it becomes a recall conversation.
This isn't a reason to panic about your cave. It's a reason to treat winter as its own testing season rather than an extension of fall.
What actually moves in winter
Three things tend to shift together once outdoor temperatures drop and indoor heat comes on: relative humidity falls, air exchange rates in older buildings often increase as staff prop doors during deliveries, and condensation patterns on cave walls and drains change as the temperature differential between inside and outside widens. Any one of those can move where moisture — and the organisms that travel with it — collects on a floor drain, a shelf edge, or a door gasket. None of it shows up in a batch record. It shows up in an environmental swab, which is the whole point of testing the room and not just the cheese. New industry guidance published this year makes the same point in different words: environmental monitoring data and the shelf-life reasoning built on it need to be scientifically defensible and proportionate to actual risk, not a copy-paste from last year's plan.
If your swab map hasn't been updated since you built your food safety plan, winter is a good prompt to walk it again. Drains, drain covers, floor mats, and any surface near a door that gets propped for deliveries deserve a look even if they weren't flagged as high-risk in the original plan. A swab result is a snapshot; what protects a facility over a season is the pattern across several snapshots, which means the plan matters more than any single test. A few things worth checking against your own written plan this month: are your swab locations still matched to where moisture and traffic actually concentrate in winter, not just where they did when the plan was written; is someone logging humidity and temperature readings on a schedule you'd actually catch a slow drift in, daily rather than "whenever someone remembers"; and does your corrective-action language say what happens on a presumptive positive, specifically, rather than "investigate and retest."
The federation's Listeria Control in Small Creameries course walks through building or tightening exactly this kind of seasonal plan, and it's a useful refresher even for members who've run a facility for years — habits drift the same way humidity does. If you want it timed to the season, our environmental-monitoring webinar later this month covers swab mapping and corrective actions in more depth; watch the events calendar for the date.
None of this is a substitute for your own written food safety plan or a qualified consultant's review of your specific facility — every building behaves differently once the furnace comes on, and a course can only teach the general pattern, not your drain.
The International Cheese Federation (ICF) and More Cheese are entirely fictional. This post is demonstration content created for MemberJunction. All people, organizations, events, courses, certifications, figures, and quotations in it are invented, and nothing here represents a real association, a real business, a real person, or real professional advice.