Three names, one fixture. When a contractor quotes a jelly jar, the electrician on site calls it a jam jar, and the spec sheet says vapor-tight, all three are describing the same sealed luminaire: an enclosed fixture with a globe or flat lens, usually behind a metal guard, sealed against moisture, dust, and corrosion. The word changes by trade and by habit, not by product. What actually changes between two of them is printed on the spec sheet: the ingress protection number, the impact rating, and whether the fixture carries a hazardous-location listing. This guide separates the slang from the spec, so you can compare a quoted vapor tight LED fixture against the vapor-tight LED fixtures (jam jar) line on a like-for-like basis instead of guessing.
Where the three names came from
Jelly jar is the oldest of the three. It describes the shape: a lamp inside a threaded glass globe with a cast guard over it, which looks like a preserving jar. The name stuck long after the lamp inside became LED.
Jam jar is the same shape and the same idea. You will hear both terms on the same job site, sometimes from the same person in the same sentence. There is no technical distinction between them.
Vapor-tight (or vapor-proof) is the only one of the three that describes what the fixture does rather than what it looks like. It means the housing is sealed so that moisture and airborne contaminants cannot reach the driver and the LED board. Because it describes a seal rather than a shape, the term also gets applied to sealed linear fixtures that look nothing like a jar.
So: jelly jar and jam jar name a shape. Vapor-tight names a property. Two fixtures can share all three words and still be built to different ratings.
"Vapor-tight" is not a rating
This is the part that costs people money. No standard defines the word vapor-tight, so it can be printed on a fixture that is sealed well and on one that is barely sealed at all. The checkable number is the IP rating, and it has two digits that mean two different things.
- First digit (solids): 6 is the top of the scale and means dust-tight, no ingress at all.
- Second digit (liquids): 5 means protected against water jets from any direction. 6 means protected against powerful water jets. 9K is a separate high-pressure, high-temperature spray test used for wash-down duty.
The EX-O2 jam jar is rated IP66 and IK08. The commercial LED Vapor Lights are rated IP65 and IK08. Both are dust-tight. The difference sits in the second digit, which is the difference between a fixture that takes a hose-down and one rated for a more forceful jet.
IK08 is the impact rating, a separate scale from IP. It matters wherever a fixture sits within reach of a forklift mast, a pressure wand, or a swinging load. A high IP number on a lens that cracks on first contact does not stay a high IP number.
The difference that is not a name: hazardous-location listing
Shape and seal are selection choices. A hazardous-location listing is not. If your area-classification drawing marks the space as classified, the fixture has to carry the matching listing or it does not go in, regardless of how well sealed it is.
The EX-O2 jam jar is listed to UL844 for Class I, Division 2, Groups A, B, C, and D, along with UL1598 for wet locations, UL1598A for marine outside type, UL8750 for LED safety, and an ABS marine listing. That is why the same series appears under both the industrial jam jar page and the Class I, Division 2 jam jar page. It is one product, cross-listed, not two versions.
The commercial LED Vapor Lights are wet-location listed fixtures for commercial duty: parking structures, canopies, garages, and production workshops. They are not hazardous-rated, and no amount of sealing makes them a substitute in a classified area. If the drawing says Class I, Division 2, the jam jar line is the one to price.
Five numbers to check before you compare quotes
Two quotes that both say "vapor tight LED fixture" are not comparable until you read these five lines.
- IP rating. IP65 and IP66 are both dust-tight but differ on water. IP69K is a different test entirely.
- Impact rating. IK08 on both lines above. If a quote does not print one, ask.
- Ambient temperature range. The EX-O2 publishes its range by temperature code: T6/T80°C from -40°C to +25°C, T5/T95°C from -40°C to +40°C, and T4/T130°C from -40°C to +60°C. The higher ambient you need, the higher the T-code you have to accept, and the T-code has to suit the classified area.
- Lens and housing material. The EX-O2 uses a copper-free aluminum housing with a choice of tempered glass or polycarbonate lens, clear or frosted, and ships with a metal guard. Copper-free aluminum matters in marine and corrosive air; the guard matters where impact is likely.
- Mounting and cable entry. The EX-O2 mounts to ceiling, pole, or wall at 90 degrees or on a rotating cap, and has four side-wall cable entries sized for M25, M20, NPT 1/2 in, or NPT 3/4 in glands or stopping plugs. Confirm the entry matches the gland you are already buying rather than adapting on site.
Jar or linear: match the format to the space
Once the rating is settled, format is a coverage question.
The jar format is compact and made for spot coverage in tight places: aisles, stairwells, walkways, loading areas, and equipment bays where a full high bay does not fit. The EX-O2 runs 15 W to 40 W with a 1,500 to 4,000 lumen output at 100 lm/W, on 120-347 VAC input, with 0-10 V dimming, CRI above 70, and a CCT choice from 2000K through 6500K. Three lengths (long, medium, short) let you match the fixture depth to the clearance you actually have. An emergency battery option with 1.5 hours of runtime is available.
The linear format covers a line rather than a point, which suits parking decks, canopies, corridors, and bench work. The LED Vapor Light 5th Gen is a 4 ft fixture at 32 W (4,400 lumens) or 40 W (5,600 lumens), with a selectable 30/40/50 W version rated 7,000 lumens, all at 140 lm/W across a 120 degree beam, on 100-277 V or 100-347 V input. The LED Vapor Light 8th Gen is the high-output version of the same idea: 4 ft, 200 W, 28,000 lumens at 140 lm/W, with a selectable 160/180/200 W variant, on 120-277 V or 120-347 V. Both offer 3500K, 4000K, and 5000K selectable color temperature and carry a 5-year warranty.
When neither one is the right fixture
If the space gets hosed down as part of a sanitation cycle rather than an occasional wash, neither an IP65 nor an IP66 fixture is the correct spec. High-pressure, high-temperature wash-down is an IP69K requirement, tested at a pressure and water temperature that IP66 never sees. That is the food processing IP69K line, and our IP69K vs IP67 explainer covers what the test actually involves. Do not let the word vapor-tight carry a fixture into a wash-down zone it was never rated for.
What to send us for a quote
Four lines get you a real price instead of a range:
- The area classification, if any, from your drawing.
- The mounting height and format you need, jar or linear.
- The ambient temperature at the fixture location.
- The cable entry and gland size already spec'd for the job.
Send those through the quote request and we will match the fixture and the listing to the zone, with the spec sheet attached.
Common questions
Is there any difference between a jelly jar and a jam jar fixture? No. They are two trade names for the same round sealed luminaire. The difference between two fixtures with either name comes from the printed ratings, IP, IK, ambient temperature, and any hazardous-location listing, not from which word the quote uses.
Does vapor-tight mean the same as explosion-proof? No, and this is the most expensive confusion in the category. Vapor-tight describes a seal against moisture and dust. A hazardous-location listing, such as UL844 Class I, Division 2, means the fixture has been tested and certified for use where flammable gas or vapor can be present. A vapor-tight fixture with no hazardous listing is not legal in a classified area. Check the listing on the spec sheet, not the word on the box.
What IP rating do I need for a vapor-tight fixture? It depends on what the fixture is exposed to. IP65 is dust-tight and protected against water jets, which covers most commercial wet locations like parking structures and canopies. IP66 adds protection against powerful water jets, which suits harsher industrial and marine exposure. If the area is washed down at high pressure and high temperature as part of sanitation, you need IP69K instead, which is a different test entirely.
Can a jam jar fixture be used in a Class I, Division 2 area? Only if that specific fixture carries the listing. The EX-O2 jam jar series is listed to UL844 for Class I, Division 2, Groups A, B, C, and D, which is why it appears on both the industrial and hazardous category pages. Other jar-shaped fixtures may carry no hazardous listing at all. Always confirm the printed listing against your area-classification drawing before ordering.
Why do vapor-tight fixtures come in both round and linear shapes? Because vapor-tight describes the seal, not the shape. The round jar format is the original, built for spot coverage in tight spaces. The linear format applies the same sealing approach to a 4 ft fixture that covers a line, which suits parking decks, corridors, and workshops. Pick the format by the coverage pattern you need, then confirm the ratings separately.
Do I need a metal guard on a sealed fixture? It depends on impact exposure, not on the seal. The IK rating tells you how much impact the fixture takes on its own; IK08 covers both lines described here. A guard is worth having anywhere a forklift mast, a pressure wand, or moving material can reach the lens, since a cracked lens ends the ingress protection immediately. The EX-O2 ships with a metal guard included in three lengths.
Sources: IEC 60529 (IP code) and IEC 62262 (IK code) rating scales; UL844, UL1598, UL1598A, and UL8750 listings as printed on the fixture spec sheets referenced above.
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