Chemical Indicator Classes in Practice: A Brand-by-Brand Comparison of Class 4, 5 and 6 Products

15 septembre 2026

CliniEco Medical sterilization pouch with Class 4 dual indicator, assorted sizes, 200-pack

Ontario's reprocessing guidance requires an internal chemical indicator inside every package, and it allows a Class 5 or Class 6 indicator to help justify releasing routine loads when quarantine is not practical. That makes Class 4, Class 5 and Class 6 the three chemical indicators a clinic actually buys — and they are not interchangeable. Under ISO 11140-1:2014, a Class 6 emulating indicator is tied to one stated cycle (for example 134 °C for 3.5 minutes), while a Class 5 integrating indicator carries stated values that correlate to a biological indicator across three time and temperature relationships. This comparison sets out what each class must do by definition, then lines up the Class 4, 5 and 6 products sold into Canada across 3M/Solventum, Crosstex, Terragene and Propper on the cycle values each manufacturer publishes.

What ISO 11140-1 actually classifies

ISO 11140-1 is the standard that defines chemical indicators for sterilization. Its current edition is 2014, and an amendment (ISO 11140-1:2014/AWI Amd 1) is in development at the time of writing. It sorts every chemical indicator into one of six classes according to what the indicator monitors.

Public Health Ontario restates those six classes in Table 2 of its provincial reprocessing guidance, Cleaning, Disinfection and Sterilization of Medical Equipment/Devices in All Health Care Settings (3rd edition, May 2013, page 39). That table is the version most Ontario inspectors and infection control practitioners work from, so it is worth reading at the level of wording rather than summary. The three classes clinics buy inside the pack are these:

Class	Definition (Public Health Ontario, Table 2, p. 39)	Stated use
CLASS IV — Multi-variable Indicator	"Indicator that reacts to two or more critical variables in the sterilization cycle under the conditions specified by the manufacturer"	Process control; example given is paper strips
CLASS V — Integrating Indicator	"Indicator that reacts to all critical variables in the sterilization process (time, temperature, presence of steam) and has stated values that correlate to a BI at three time/temperature relationships"	Process control; "may be used as an additional monitoring tool to release loads that do not contain implants"
CLASS VI — Emulating Indicator	"Indicator that reacts to all critical variables (time, temperature, presence of steam) for a specified sterilization cycle (e.g., 10 min., 18 min., 40 min.)"	Internal CI for process control; "a different Class VI emulating indicator is required for each sterilization cycle time and temperature used"; "cannot be used as an additional monitoring tool to release loads that do not contain implants"

The classes either side of those three matter too: Class I covers process indicators such as autoclave tape and indicator labels applied to the outside of a package, Class II covers indicators used in specific test procedures such as the Bowie-Dick air removal test, and Class III covers single-variable indicators such as temperature tubes. Autoclave tape is therefore a chemical indicator, but it answers one question only: was this pack exposed to a cycle?

Where each class sits in an Ontario monitoring routine

Chemical indicators are one of three monitoring layers, alongside physical parameters and biological indicators, and the requirements apply at the same time rather than as alternatives:

Monitoring layer	What Public Health Ontario requires (pp. 40–41)
Internal chemical indicator	"An internal chemical indicator shall be placed inside each package, container or bundle that is undergoing sterilization in the area judged to be least accessible to steam penetration or to the sterilizing agent"; "the class of indicator chosen is based on the parameters being measured and the degree of precision that is needed"
External chemical indicator	"Each package or container to be sterilized shall have an externally visible Class I chemical indicator, which is examined immediately after sterilization"
Air removal (dynamic air removal sterilizers)	"an air removal test with a Class II chemical indicator shall be performed every day the sterilizer is used"
Biological indicator	"A biological indicator shall be used to test the sterilizer each day that it is used and with each type of cycle that is used that day"; a BI is also required in every load containing implantable devices

Two sentences in the same document constrain how far any chemical indicator can be pushed. Public Health Ontario states that "chemical indicators do not replace the need to use a biological indicator", and that they "do not indicate that a device is sterile ... but do indicate that the package has been processed through a sterilization cycle." The daily testing obligation sits with the biological indicator; the internal chemical indicator answers a narrower question — whether conditions were reached at the least accessible point of that package.

CliniEco Medical 24-hour self-contained biological indicator, 25-pack, for steam sterilizer monitoring

Class 4, 5 and 6 by brand: what each manufacturer publishes

The table below lists what each manufacturer states in its own product documentation, including the cycle values or operating range, the physical format, and the pack counts. Where a brand does not publish a detail, the cell is left blank rather than filled with an assumption.

Product (part number)	Brand	Class	Published cycle values or range	Format	Pack count
Comply Steam Chemical Indicator Strip 1250	3M / Solventum	4	"monitor all 121-134 °C (250-273 °F) gravity and vacuum-assisted steam sterilization cycles"	Paper strip 1.5 cm × 20 cm; indicator ink turns off-white to black	240 per carrier; 8 carriers per case (1,920 per case)
Comply SteriGage Steam Chemical Integrator 1243A	3M / Solventum	5	Internal pack monitor for steam cycles (wick-style moving front)	1.9 cm × 5.1 cm (3/4 in × 2 in)	500 per bag; 2 bags per case (1,000 per case)
8 in Steam Indicator Strip (SIL-250)	Crosstex	4	Steam; irreversible colour transition from blue to dark	203 mm × 16 mm (8 in) strip, perforated so it can be torn for smaller packs	250 per bag
STEAMPlus Sterilization Integrator (SSI-100 / SSI-1000)	Crosstex	5	"Reacts to all three parameters of sterilization (time, temperature, saturated steam)"; operation range 121 °C to 135 °C	101 mm × 19 mm (4 in × 0.75 in) wick strip, immediate read-out	100 per bag (SSI-100); 1,000 per bag (SSI-1000)
EmPlus 134 Emulator (EMP-1004)	Crosstex	6	"For use in pre-vacuum steam sterilizers operating at 134 °C for 3.5 minutes or longer"; indicator turns from green to brown	101 mm × 19 mm (4 in × 0.75 in)	1,000 per bag
Integron IT26-1YS Chemical Integrator	Terragene	5	"Validated for gravity displacement cycles (121 °C/30 min, 132 °C/15–25 min, 135 °C/10 min) and dynamic air removal cycles (132 °C/4 min, 135 °C/3 min)"; yellow to black	One-side laminated strip; calibrated against kill time of 10⁶ Geobacillus stearothermophilus in a BIER resistometer	Not published on the product page
Integron IT28 3 Point Emulator	Terragene	6	Dual emulation conditions: "3.5 minutes, 134 °C // 15 minutes, 121 °C"; blue to black	One-side laminated card; non-laminated side for writing load records	Not published on the product page
VAPOR LINE Steam Chemical Integrator (C5-V250)	Propper	5	"Type 5 Chemical Integrator for Steam Sterilization, use for pack and load monitoring, compliant with ISO 11140-1:2014"; for cycles at 121 °C, 132 °C and 134 °C	Moving-front ink strip with printed PASS and FAIL areas, 2 in	250 per bag
Sterilization Pouch with Class 4 dual indicator	CliniEco Medical	4 (plus Class I external indicator)	Steam; dual indicator printed on the pouch (external process indication plus internal multi-variable indication)	Self-seal pouch, assorted sizes	200 per pack

Two patterns stand out in those rows. The Class 5 products publish a range: Crosstex states 121 °C to 135 °C for STEAMPlus, Propper's VAPOR LINE is stated for 121 °C, 132 °C and 134 °C cycles, and Terragene lists the gravity and dynamic air removal cycles its IT26-1YS is validated for. The Class 6 products publish one or two specific cycles, because that is what a Class 6 indicator is: an emulator of a stated cycle.

The passage that decides load release — and the tension inside it

The operational consequence of choosing between Class 5 and Class 6 is release authority, and this is where the guidance needs to be read closely rather than skimmed.

Page 41 of the same document states, under biological monitoring: "Items in the processed load should not be released until the results of the BI test are available; if quarantine pending BI results is not possible, evaluation of a Class 5 or 6 chemical indicator and the specific cycle physical parameters may be used to justify the release of routine loads." The next bullet adds that "implantable devices shall be quarantined until the results of the BI test are available."

Table 2 on page 39, however, attaches a direct limitation to the emulating class: a Class VI emulating indicator "cannot be used as an additional monitoring tool to release loads that do not contain implants." A Class V integrating indicator "may be used" for that purpose.

The two passages sit in tension, and the practical way to handle it is to write the conservative reading into your policy and record it: a Class 6 indicator documents that a stated cycle ran as specified, but it is not the basis on which a routine load leaves quarantine. If your clinic relies on chemical evaluation to release routine loads when a biological result is not yet available, the indicator the guidance names for that purpose is a Class 5 integrator, evaluated with the cycle's physical parameters and recorded as such. Implant loads wait for the biological result either way; page 37 notes that processed items may be identified with external chemical indicators such as autoclave tape, which distinguishes processed from non-processed rather than indicating sterility.

CliniEco Medical autoclave indicator tape, Class I external process indicator for steam sterilization packs

Why Class 6 lines multiply and Class 5 lines do not

If a clinic runs more than one steam cycle — a 134 °C pre-vacuum cycle for wrapped instruments and a 121 °C gravity cycle for heat-tolerant items, for instance — the Class 6 decision is per cycle. Public Health Ontario states it directly: "a different Class VI emulating indicator is required for each sterilization cycle time and temperature used." Two cycles means two emulating SKUs, each with its own storage, expiry and stock rotation.

A Class 5 product covers the range. Terragene's published validation for the IT26-1YS enumerates it: gravity displacement cycles at 121 °C/30 min, 132 °C/15–25 min and 135 °C/10 min, plus dynamic air removal cycles at 132 °C/4 min and 135 °C/3 min. That is one part number across the cycles a general practice or a small long-term care reprocessing room is likely to run.

The trade-off is not quality: a Class 6 indicator is calibrated to one cycle and can be more precise within it, while a Class 5 spans the range with stated values that correlate to a biological indicator at three time and temperature relationships. For most clinics the deciding factors are how many cycle types are in use and whether the indicator will be asked to support a release decision.

What to write on the purchase order

Indicator specifications are often reduced to "Class 4 strips" or "Class 5 integrators", which leaves the details that matter open. Ask for these in writing:

The ISO 11140-1 class, and the standard edition the claim is made against. "Type 4 per ISO 11140-1:2014" is a checkable statement; "Class 4 strips" is not.
The cycle values or operating range. For a Class 6 product this is the stated emulation condition, for example 134 °C/3.5 min. For a Class 5 product it is the range or the list of validated cycles.
The format and dimensions, measured against where the indicator has to sit. The internal indicator goes in the area judged least accessible to steam penetration, which is not always the centre of the package; a 203 mm strip and a 20 mm dot are not interchangeable in a small cassette.
Pack count, case configuration, storage conditions and expiry, so annual quantities can be calculated against the testing schedule.

For clinics working out what an indicator and a spore testing schedule cost per year at one, two, four or eight sterilizers, the arithmetic for both an open-system and a locked-system path is set out in our cost model by clinic size. For the wider monitoring picture, the RCDSO sterilization monitoring requirements explain how the daily Ontario rule differs from the weekly baseline used in the United States.

Clinics that want to compare formats on their own sterilizer can use a Class 4 pouch with a dual indicator for package-level monitoring, and a 5-pack biological indicator trial alongside a 24-hour self-contained indicator, 25-pack to run the biological layer of the same schedule. These are optional references for readers comparing formats; nothing on this page depends on them.

Ordering for a clinic, lab or care home? Wholesale and multi-site ordering covers case pricing and account setup, and the B2B wholesale collection lists the lines stocked for institutional buyers.

Related reading

Sterilization compliance hub — the monitoring, packaging and record-keeping requirements collected in one place
ISO 11140-1 explained: the six classes of chemical indicators — the class definitions themselves, class 1 through 6
Class 4 vs Class 5 vs Class 6 chemical indicators: which to use in Canada — the selection decision for a Canadian clinic
Indicator tapes compared: 3M Comply, Crosstex and clinic alternatives — the Class I layer that sits on the outside of the pack
Biological vs chemical indicators — why one cannot replace the other
Rapid Readout Biological Indicator Readers: Every Major Brand Compared (2026 Canada Price Guide)
The Real Annual Cost of Biological Monitoring: Locked Ecosystems vs Open-System BIs in Canadian Dental Clinics
free Ontario sterilization compliance log

Frequently Asked Questions

Is a Class 6 emulating indicator better than a Class 5 integrating indicator?

They answer different questions. A Class 6 emulating indicator reacts to all critical variables for one specified sterilization cycle, and a different Class VI indicator is required for each cycle time and temperature used. A Class 5 integrating indicator reacts to all critical variables across the process and carries stated values that correlate to a biological indicator at three time and temperature relationships. Class 6 is narrower and cycle-specific; Class 5 spans cycles.

Can a chemical indicator release a load without waiting for the biological result?

For routine loads that do not contain implants, Public Health Ontario allows evaluation of a Class 5 or Class 6 chemical indicator together with the cycle physical parameters to justify release when quarantine is not possible. Implantable devices must be quarantined until the biological result is available. Table 2 of the same document also states that a Class VI emulating indicator cannot be used to release loads that do not contain implants, so a policy that relies on chemical evaluation to release routine loads should name a Class 5 integrator.

Does an internal chemical indicator replace the daily spore test?

No. Public Health Ontario states that chemical indicators do not replace the need to use a biological indicator and do not indicate that a device is sterile. The biological requirement is separate: a biological indicator is used to test the sterilizer each day it is used and with each type of cycle used that day, and in every load containing implantable devices.

Which class of chemical indicator has to go inside every package in Ontario?

The class is chosen rather than fixed. Public Health Ontario requires an internal chemical indicator inside each package, container or bundle, placed in the area judged to be least accessible to steam penetration, and states that the class chosen is based on the parameters being measured and the precision needed. A Class 4 multi-variable indicator is the common choice for a wrapped instrument pack.

Does autoclave tape count as a chemical indicator, and which class is it?

Yes. Autoclave tape is a Class I process indicator applied to the outside of a package. It shows that the pack was exposed to a cycle and differentiates processed from non-processed items; it does not show that steam penetrated the pack or that the contents are sterile. Public Health Ontario requires an externally visible Class I indicator on each package or container, examined immediately after sterilization.

How many Class 6 indicator part numbers does a clinic with two steam cycles need?

Two, unless one product covers both, because the emulating class is tied to stated cycle values: a 134 °C pre-vacuum cycle and a 121 °C gravity cycle each need an indicator that emulates those conditions. Terragene's IT28 publishes two emulation conditions on a single part number, at 134 °C for 3.5 minutes and 121 °C for 15 minutes; a Class 5 integrator such as IT26-1YS or Crosstex STEAMPlus covers a range instead.

Can a Class 4 pouch indicator tell me a load is sterile?

No. A Class 4 multi-variable indicator reacts to two or more critical variables under the conditions specified by the manufacturer. On a dual-indicator pouch it confirms exposure and that conditions were reached at the indicator's position. Public Health Ontario is explicit that chemical indicators show a package has been processed through a sterilization cycle, not that a device is sterile.

CliniEco Medical is a Canadian medical device establishment with MDEL #35334, supplying sterilization monitoring and infection control consumables. This comparison reproduces the wording published by the standard and public health bodies cited below; where a manufacturer does not publish a specification, it is shown as unpublished rather than estimated.