by Neville McNaughton aka Dr. Cheese
Food Safety is about consciousness. If we understand it we can improve it. This brings me to the topic of drips and their causes.
Overhead drips in production spaces represent a failure of design, regulation and pragmatism. The source of overhead drips of water are very few, but they are a predictable consequence of design.
Over many years I have observed the construction of many cooler spaces and aging rooms that show drips from the ceilings, a very serious direct food safety hazard when exposed products are present in the space. Drips in most cooler and aging spaces are primarily a function of a failure of the vapor barrier on the outer skin of the cooler space. The other possible failure is the moisture barrier. When water is present on the top of the cooler's outer ceiling and there is no seal on the top of the ceiling, your space is exposed to water from leaking pipes, dripping condensate, or a leaking roof. Let's take a look:
Cause #1: A failure of the vapor barrier in the ceiling of the cooler space.
Vapor exists in air when there is sufficient energy to ensure it maintains its vapor state. Such a condition would be 85 degrees F, 85% RH, which equates to a Dew Point of 75 degrees F. Vapor is attracted to low temperature surfaces, and when it makes contact with those surfaces it will condense.
An example is an aging room or cooler at 55 degrees F, which is 20 degrees below the 75 degree F Dew Point example. When this air contacts the cool surface it turns to water. This high Dew Point, moisture laden air finds its way down through insulation, through timber structural members, mounting rods, cracks, holes, punctures in vapor barriers etc. When building a cooler it is critical to have the vapor barrier on the outer surface, ceilings and walls, and to some extent, the floors.
Water accumulating above the ceiling eventually finds its way down. If there is a vapor barrier on the inside and it cannot leak through, it will build up on the top of the ceiling and either find its way to the walls or become so heavy the ceiling will collapse. Collapses in licensed facilities are much more common across the U.S. and Canada than you might know. Catastrophic failures are common and product is at risk. Why does this occur? Lack of design expertise.
It is not technically possible to build a functional cooler when you integrate the exterior frame of the cooler into the building structure. We know this, so why do we do it? Right now I can identify several new cheese facilities that are being constructed this way which will eventually fail. So the reasons for building this way are perplexing.
Common justifications are:
"So and so did it this way."
"There is nothing in the regulations to say I cannot do it this way."
"My inspector does not have a problem with it."
There are many facilities throughout the food industry that are under designed and under built on some level, and most all are "approved" facilities. With the high profile failures that are occurring regularly in the food industry, attention should be drawn to the reality that many structures in which we produce food are not purpose built and are deficient on many levels. The fact that it is possible to build substandard structures should be a concern to all of us.
Cause #2: A failure of the moisture barrier in the ceiling of a production space.
When water has access down into a space, there is a likely chance it can carry with it residues of feces and urine from insects, rodents, birds or other life forms which have access to what is typically a poorly controlled space.
A primary cause of this is the failure of moisture barriers on the inside of the production space. During colder months of the year, for instance, it is not uncommon for the space above the ceiling to become very cold. Production spaces themselves are frequently hot and humid, and this humidity/vapor will be attracted to the cold conditions above the ceiling. It will naturally condense on any surface in the attic space that is below the Dew Point, accumulating water on top of the ceiling, which can then drip back down through any available crack/deficiency in the ceiling.
The moisture/vapor barrier must be on the warm side of the wall or ceiling, in this case the production side.
Cause #3: A surface in the room that is below the Dew Point attracting moisture.
Cooling systems are of many designs. Hidden, ducted systems that discharge cool air into the production environment are frequent causes of drips from the ceiling area. To cool a room, the return air is often many degrees colder than the air already in the room. This Sensible cooling process can produce a duct ceiling register with a localized temperature of easily 10 - 20 degrees F lower than the room it is cooling.
In a room operating at 70 degrees F producing product, a 50 degrees register temperature is quite common. In a room operating at 70 degrees F and a humidity above 50%, the register will be below the Dew Point and drips will form. It is not uncommon to see large stainless steel drop down ducts with registers in the sides to be at risk. Systems in less sophisticated facilities often have discharge registers above areas where high humidity is created, making drips inevitable. The #1 reason this happens is because the HVAC provider is not working with a knowledgeable customer. As a result the contractor will install typical commercial equipment.
Another scenario is the use of direct expansion equipment in an aging room or walk-in cooler where the condensate tray can become very cool. It only takes the door to be opened for a few minutes and warm, moist air will rush into the cooler and condense on the cold condensate tray. Similar conditions occur in aging rooms where all attempts to control drips should be mitigated.
Passive cooling systems mounted on ceilings and walls are prone to drips. As condensation forms on these cold surfaces, great care must be taken to prevent drips falling to the floor. A condensate tray beneath the cooling surface is critical; however when relative humidities are high, even the condensate tray can be below the Dew Point.
To sum up: drips are a problem. They are a function of design, and with good design, they can be eliminated. What will it cost? There is no simple answer, but when purchasing a system ask for design and price. Most importantly get quotes from contractors who approach the task in different ways. Air systems are changing so don't accept the first solution that is offered. Multiple quotes for the same design will not necessarily produce a better result.
On the regulatory front it is wrong to assume that your inspection service at any level will steer you clear of all costly errors. While there is evidence that regulators are aware of issues pertaining to air quality, they are not into engineering systems. Their check list is short and useful and should be taken into account, but going beyond the minimum can produce some highly beneficial results.
Finally, be pragmatic in your approach to Air and Construction. Bad design could lead to the loss of your business because it could cause a fatal recall. Cost encompasses many factors. In the case of Air, it is installation cost, sanitation, efficiency, compliance, cost over time, and functionality (absence of drips). Weighing all costs is a special skill. Balancing functionality with a budget is the trick.
