How are boxes typically kept while being mailed?

March 17, 2019 10:13 AM

I am shipping something that would ideally stay in a specific temperature range. I know about heat packs and cold packs and overnight shipping, but this question is not about any of that. I just want to know - when a box is shipped, what does its transit tend to look like from a temperature perspective around the outside of the box?

Are boxes stored outside or in non-temperature-regulated spaces for a length of time, or are they basically in temperature-regulated spaces (indoors or in vehicles that soon warm up/cool down to the driver's comfort levels) of about 65-80F for most or all of their journey up until arrival? If they are exposed to unmediated outdoor temperatures - for what duration of time is that the case?

I'm interested in USPS, FedEx, and UPS practices. I'm specifically asking about domestic shipping within the US but usually from at least a couple states away.

posted by vegartanipla to Shopping (7 answers total)

Best answer: Assume exposed. When I worked at FedEx, the temperature inside the sorting facilities and trucks was pretty similar to whatever the outside temperature was. In the summer, the aluminum trucks were ovens. Not sure they even had air conditioning.
posted by postel's law at 10:27 AM on March 17, 2019 [4 favorites]

You could probably get a better idea by shipping a few cheap USB temperature loggers along the routes you were interested in. This would also let you evaluate the effectiveness of whatever temperature stabilization methods you intend to use.
posted by flabdablet at 10:32 AM on March 17, 2019 [8 favorites]

Best answer: Depends on how they ship it, but basically always assume it will not be in AC for any length of the trip. The vast majority of trailers are not air conditioned. It's not uncommon for one to sit, loaded, on a dock for a day. Postel is right, those trailers heat up quickly in the sun.

And if it flies, Odin is right that it very likely won't be heated
posted by Jacen at 10:33 AM on March 17, 2019 [2 favorites]

I know about heat packs and cold packs and overnight shipping

Do you know about phase change temperature stabilization materials?
posted by flabdablet at 11:01 AM on March 17, 2019

Best answer: i used to work on loading docks and did some side research on warehouses. it's not unusual for these facilities to hit the high temp for the area and then remain there even after the area cools down. so let's say the high is 100F for an hour, you could get 90-110F in a warehouse for 4 or more hours. they are great at collecting heat but for security reasons have terrible ventilation (you can't open the bay doors to cool places off because management is worried about theft).

so: assume you'll see approx the extreme temps of a given area, but longer.
posted by zippy at 12:46 PM on March 17, 2019 [1 favorite]

It really depends on the time of year and route - and a whole host of other day-to-day factors.

I really like flabdablet's idea about sending a temperature monitor along the route your interested in. Is the shipment uniform? How big is the package? The temperature achieved on the outer edges might very well be different from in the middle of the box, depending on the thermal mass of the contents.

In the past I've used shipping damage indicators for temperature - one on the bottom of the box, one near the center if accessible, and one on the inside of the top flap. If the temperature goes outside (either above or below) a certain range (and there are a ton of ranges available), there is an irreversible chemical reaction that can be read visually.
posted by porpoise at 1:02 PM on March 17, 2019 [3 favorites]

Best answer: I have done lots of shipping studies where we did put those trackers in and on the outside of packages. Both international and domestic (us) shipments. The packages got very hot in summer (100-120f) and very cold in the winter. Even overnight domestic packages. Usually, no colder in the winter than whatever the temperature was but in summer, things got much hotter than 'ambient'. Also, based on the fact that we receive a lot of temperature sensitive material from outside sources (who don't always insulate it), I think these extrêmes are common.
posted by Tandem Affinity at 6:57 PM on March 17, 2019 [5 favorites]