Vacuum Sealing Mylar Bags: Chamber vs. External Sealers

Vacuum sealing Mylar bags depends on two things that are easy to overlook: the bag's construction and the kind of sealer you own. A machine may make a good heat seal across a bag without removing the air inside it. Those are different outcomes.

For the flat, 7-mil LEM Mylar bags we carry, LEM's current guidance is clear: an appropriate chamber machine can vacuum-seal them, while an external suction machine can heat-seal them but does not vacuum-seal them. Start with that distinction before choosing a machine or filling a batch of bags.

Heat sealing and vacuum sealing do different jobs

Heat sealing closes the bag's compatible inner sealing layer. Vacuum sealing also removes air as part of the machine's packaging cycle. A flat-looking pouch or a firm seal line alone does not prove that air was removed successfully.

External suction sealers normally draw air through the bag opening. They need a bag construction approved for that process. Chamber machines place the bag inside a chamber and use a different pressure cycle. The word Mylar describes neither a universal air channel nor a guarantee that every bag works in every machine.

Match the bag construction to the machine

See LEM's flat Mylar bag guidance for the controlling product distinction. Do not add improvised strips, punctures or accessories to force a flat pouch to work unless the manufacturers expressly approve the method.

Check the filled bag against the chamber

Bag width is only the first measurement. A filled pouch must fit within the chamber while leaving its opening correctly positioned on the seal bar. A bag that fits flat on a counter can become awkward once filled with bulky food.

Compare the LEM MaxVac Pro and MaxVac Pro+ using their exact chamber dimensions, seal-bar specifications and instructions. The largest bag sold is not automatically the best bag for either machine.

Choose portions around how you cook and rotate food. Several manageable packs may be easier to inspect and use than one overfilled pouch. Leave the filling and sealing space required by the equipment instructions; do not invent a universal headspace measurement across different machines and foods.

Use model-specific seal settings

Thicker packaging can require different sealing conditions from ordinary vacuum bags. That does not mean turning every machine to its highest setting. Obtain the bag supplier's guidance for the exact sealer, and follow the machine's cooling intervals and duty limits.

Keep the sealing area clean, dry and free from creases or food particles. Inspect completed seals and stop to investigate inconsistent results before packing a large quantity. A successful seal on one sample is a reason to check the process carefully, not a guarantee for an entire batch.

For choosing between the two chamber machines more generally, use our MaxVac Pro versus Pro+ comparison.

Choose the food-storage method before the packaging

A barrier pouch does not make moist food shelf-stable. Utah State University Extension explains that vacuum packaging is not a preservation method by itself: food that needed refrigeration or freezing before packaging still needs it afterward. Removing oxygen can increase the risk from certain pathogens.

For dry staples and properly dried foods, follow food-specific storage guidance. An oxygen absorber removes oxygen; it does not remove moisture or validate that food is dry enough. Select absorber capacity and packaging using appropriate instructions rather than a blanket packet size for every pouch. Keep absorbers away from children and follow their handling directions.

The LEM flat bags discussed here are not approved for boiling or microwaving. Do not transfer sous-vide or heating claims from a different chamber-bag product just because both fit the same machine.

Label, protect and rotate the finished packs

Record the food, packing date and any preparation information you need later. Store packs under conditions appropriate to the food, protect them from punctures and pests, and inspect them during rotation. Do not assume every food receives the same shelf life from the same pouch.

Browse vacuum sealers and compatible packaging with your bag type, filled dimensions and food-storage plan in hand. The right match begins with understanding whether you need a heat seal, a vacuum cycle or a different preservation method altogether.