Application Note · Medical Equipment
AD16-22 Indicator Lights in Medical Equipment: Where They Are Used, What They Signal, and the Limits You Must Respect
A Φ22 industrial pilot light inside a medical device stops being just a lamp. A practical guide for equipment manufacturers, panel builders and hospital engineering teams — plus the boundaries set by IEC 60601 that decide where it may never be installed.
MONTOLI Technical Team | Updated October 2026 | 11 min read | Medical Equipment
Key takeaways
- AD16-22 is an industrial Φ22 pilot light (IEC 60947-5-1). The moment it is built into medical electrical equipment it becomes part of a system that must satisfy IEC 60601-1 — leakage current, creepage and clearance are judged at equipment level, not at lamp level.
- Its real applications are on equipment cabinets, operator consoles, facility panels and medical IT power systems — not in the patient environment and not on applied parts.
- Medical use adds requirements industrial panels rarely face: resistance to hospital disinfectants, sealed fronts for fluid ingress, alarm-colour discipline (IEC 60601-1-8), EMC (IEC 60601-1-2), and — near MRI — non-magnetic construction.
- Four zones are off limits: the patient environment, the sterile field, inside the MRI 5-gauss line for standard ferrous designs, and oxygen-enriched or flammable anaesthetic atmospheres.
What's inside
1. Industrial component, medical system: where the responsibility sits2. A map of medical equipment and facilities3. Seven places where AD16-22 indicators do real work4. What the lamp actually does in a clinical setting5. Selection requirements specific to medical use6. Where an industrial pilot light must not be installed7. Procurement and acceptance checklist
A Φ22 pilot light is one of the most ordinary components in a control panel. Put it on a medical device and it stops being ordinary: it now sits inside equipment governed by IEC 60601-1, in rooms cleaned several times a day with aggressive disinfectants, next to patients who cannot be allowed to touch a live part, and sometimes a few metres from an MRI magnet.
This article maps where AD16-22 type indicators genuinely appear in medical equipment and healthcare facilities, what each one signals, the extra requirements that medical use imposes, and the four zones where an industrial pilot light must never be installed.
1. Industrial component, medical system: where the responsibility sits
AD16-22 is a Φ22 mm panel-mounted LED indicator built to the industrial low-voltage control standard. It has no medical approval of its own, and none is claimed. What changes is the context: the finished equipment is assessed as a whole, and the lamp becomes one element in that assessment.
| Question | What it means in practice |
|---|---|
| Which standard applies to the lamp itself? | IEC 60947-5-1 / GB/T 14048.5 as an industrial control-circuit device. There is no "medical grade" version of the lamp. |
| Which standard applies to the equipment? | IEC 60601-1 (general safety), IEC 60601-1-2 (EMC), IEC 60601-1-8 (alarm systems), plus particular standards for the device type. |
| Who ensures creepage, clearance and leakage current? | The equipment manufacturer, at equipment level. A lamp fed from a SELV circuit (typically 24 V DC) generally makes this far easier than one fed from mains. |
| Can the lamp touch the patient? | No. Anything in the patient environment or on an applied part falls under much stricter requirements and is outside the scope of an industrial panel device. |
| What does the supplier provide? | A datasheet with all rated fields, declaration of conformity, RoHS/REACH statements, material declarations — the evidence the manufacturer needs for its technical file. |
Commercial point worth repeatingNever present an industrial pilot light as "medical approved". What you can honestly offer is a well-documented component plus the support the equipment manufacturer needs for its own 60601 assessment. That distinction is what wins repeat orders from medical OEMs.
2. A map of medical equipment and facilities
| Area / equipment type | Where the lamp sits | What it signals |
|---|---|---|
| Imaging systems (CT, X-ray, DR, ultrasound carts) | System cabinets, gantry-side local panels, operator console panels | Power on, self-test passed, exposure enabled, interlock closed |
| Radiotherapy and treatment equipment | Control cabinets, treatment room door panels, console panels | Beam on, door interlock, treatment ready, emergency off latched |
| Patient treatment devices (dialysis, infusion stations, ventilator workstations) | Equipment front panels and mobile cart panels | Therapy running, alarm, mains/battery, service required |
| Laboratory and diagnostic analysers | Instrument panels, reagent and waste compartments, sample-handling modules | Run in progress, reagent low, waste full, cover interlock |
| CSSD — sterilizers and washer-disinfectors | Machine front panels (not inside the chamber) | Cycle running, cycle complete, sterilant present, door locked |
| Medical gas and vacuum systems | Area alarm panels for oxygen, nitrous oxide, medical air, surgical vacuum | Normal, high/low pressure, changeover to reserve, fault |
| Medical IT power systems in clinical rooms | Insulation monitoring and fault indication panels serving the operating theatre or ICU | Insulation fault, overload, transformer temperature |
| Hospital infrastructure | UPS and distribution boards, technical room panels, nurse-call power panels | Source selected, battery discharge, earth fault, load on |
3. Seven places where AD16-22 indicators do real work
Location 1 — Imaging system cabinets and operator consoles
Where exactlyPower and control cabinets of CT, X-ray and DR systems, plus the local panel on the operator console. Outside the exposure room's controlled area unless the design specifically places it there.
What it signalsSystem powered, self-test passed, exposure enabled, door/interlock closed, fault.
Why it mattersTechnicians check cabinet state before a service intervention. A local lamp answers "is this cabinet still energised?" without opening a door or waiting for a workstation to boot.
Location 2 — Radiotherapy and treatment-room door panels
Where exactlyControl cabinets and the panel beside the treatment-room door; the classic amber/red pair for "beam on". Not inside the treatment head or the beam path.
What it signalsBeam on / radiation in progress, door interlock closed, emergency-off latched, treatment ready.
Why it mattersThis is a safety-relevant indication with strict semantics. The lamp must be duplicated or backed by a feedback contact: a single lamp that fails dark would be dangerous, because staff would read it as "no radiation".
Location 3 — Dialysis, infusion stations and ventilator workstations
Where exactlyFront panels of treatment devices and the panels of mobile carts and bedside workstations.
What it signalsTherapy running, alarm active, mains versus battery operation, service due.
Why it mattersFrequent disinfection. Select a smooth, sealed front face (IP65 with gasket) and confirm the lens and gasket resist the alcohol, chlorine-based and quaternary-ammonium agents used in the department.
Location 4 — Laboratory analysers and sample-handling modules
Where exactlyInstrument panels: run status, reagent compartment doors, waste compartments, sample-handling covers.
What it signalsRun in progress, reagent low, waste container full, cover or interlock closed.
Why it mattersRuns are long and often unattended; staff glance at the instrument from across the lab. Colour meaning must be consistent across every instrument in the laboratory so a new shift reads it the same way.
Location 5 — CSSD sterilizers and washer-disinfectors
Where exactlyMachine front panels in the central sterile services department — never inside the sterilizing chamber or in the hot zone.
What it signalsCycle running, cycle complete, process medium present, door locked.
Why it mattersHeat, saturated steam and chemical residues are the norm. Pay attention to gasket material, terminal corrosion and periodic inspection; humidity and chemical vapour kill panel devices well before the LED does.
Location 6 — Medical gas and vacuum area alarm panels
Where exactlyArea alarm panels for oxygen, nitrous oxide, medical air, surgical vacuum and AGSS, plus plant-room panels for the source equipment.
What it signalsNormal, pressure high/low, emergency reserve in use, changeover occurred, fault.
Why it mattersClinical staff rely on these panels. Note the environment: oxygen-enriched atmospheres change the rules for materials and ignition sources, so any component specified there must be assessed for that specific condition.
Location 7 — Medical IT power systems in clinical rooms
Where exactlyPanels with insulation monitoring devices that serve the medical IT (isolated) power system of an operating theatre, ICU or cardiac catheterisation room.
What it signalsFirst insulation fault, overload, transformer temperature, system normal.
Why it mattersIn a medical IT system the supply continues to run after a first fault, so the indication is what tells the clinical engineering team to act. Prefer 24 V DC (SELV) indication here and keep the indication independent of any network.
4. What the lamp actually does in a clinical setting
| Function | What it provides | Where it is decisive |
|---|---|---|
| Independence from software | State that survives a frozen HMI, a network outage or a rebooting workstation | Imaging consoles, treatment devices, ICU |
| Safety-relevant status | Visual warning of beam on, radiation, motion enabled, interlock bypassed | Radiotherapy, imaging, treatment rooms |
| IT-system fault indication | First insulation fault on a medical IT supply, which keeps running by design | Operating theatres, ICU, catheterisation labs |
| Gas and vacuum status | Normal versus fault on oxygen, medical air, surgical vacuum and reserve changeover | Wards, theatres, plant rooms |
| Process and cycle state | Sterilization or washing cycle running, complete, door locked | CSSD |
| Maintenance and service state | Service due, bypass active, local control engaged | Every department with biomedical engineering support |
5. Selection requirements specific to medical use
| Requirement | Why it matters more here | What to specify |
|---|---|---|
| Disinfectant resistance | Panels are wiped several times a day with alcohol, chlorine-based and quaternary agents; hydrogen-peroxide vapour is common in some areas | Smooth, wipeable front; confirm lens and gasket compatibility with the agents used; sealed front (IP65 with gasket) |
| Ingress protection | Fluid spills and spray cleaning are routine near patients and in CSSD | IP65 front with the gasket correctly fitted; check panel flatness and torque at installation |
| Electrical safety at equipment level | Leakage current, creepage and clearance are judged for the whole equipment | Prefer SELV supply (typically 24 V DC) for indication; keep mains-voltage lamps out of the patient vicinity; document the assessment in the technical file |
| Alarm colour discipline | IEC 60601-1-8 defines alarm priorities and their visual coding; ad-hoc colours cause misreading | Fix the colour-to-priority mapping in the design file and keep it identical across the product family |
| EMC behaviour | Medical EMC requirements (IEC 60601-1-2) are tighter than industrial ones | Low-current LED lamps add negligible emissions; keep indication wiring short and separated from sensitive analogue circuits |
| MRI proximity | Standard designs contain ferrous parts (nuts, screws, terminals) | Do not install standard designs inside the magnet room; where indication is needed near MRI, use a verified non-magnetic construction and always outside the controlled area defined by the site |
| Traceability and documents | Technical files and audits need to show exactly what is installed | Datasheet with all rated fields, declaration of conformity, RoHS/REACH statements, material declarations, batch traceability |
| Redundancy for safety-critical signals | A lamp can fail dark, which reads as "safe" | Duplicate the indication or add a feedback contact read by the control system; never rely on one lamp for beam-on or radiation state |
6. Where an industrial pilot light must not be installed
- In the patient environment or on applied parts. Anything a patient can touch, or that forms part of the applied part, is governed by requirements an industrial panel device is not designed to meet.
- In the sterile field. Instrument tables and the sterile operating area are not places for general-purpose panel hardware.
- Inside the MRI magnet room for standard ferrous designs. Standard Φ22 devices contain steel nuts, screws and terminals. Inside the magnet room — and certainly inside the 5-gauss line — a ferrous part is a projectile and an image artefact risk. Use only verified non-magnetic constructions, and only where the site's MRI safety rules permit.
- In oxygen-enriched or flammable anaesthetic atmospheres. Oxygen enrichment changes ignition behaviour of materials. Components in such areas must be assessed for that condition; a general-purpose industrial lamp is not automatically acceptable.
- As the only indication of a critical alarm. "Beam on", "radiation in progress" and insulation-fault indications must be duplicated or fed back to the control system, so a failed lamp is itself detected.
The failure mode that mattersAn indicator used for a safety-relevant state can fail dark. Unlike a screen, it gives no error message — it simply looks safe. That is why duplication or a feedback contact is not optional for radiation, beam-on and insulation-fault indication.
7. Procurement and acceptance checklist
| Stage | Check | Acceptance criterion |
|---|---|---|
| Specification | Mounting diameter (Φ22), function, colour, voltage and current type, terminal type, front protection | All six fields on the purchase order and datasheet; SELV preferred |
| Sample approval | One sealed reference sample per variant | Colour, brightness, mechanical fit and disinfectant wipe test approved |
| Compliance documents | Declaration of conformity, RoHS/REACH statements, material declarations | Received before bulk shipment and archived with the batch ID |
| Incoming inspection | Visual condition, colour match to the reference, light-up test, gasket present | No deviation from the approved sample |
| Installation | Correct cut-out, de-burred panel, gasket seated, torque to datasheet, colour verified against the design file | Torque recorded; no mixed voltage variants in one cabinet |
| Service documentation | Specification label inside the panel door, entry in the service manual and spare-parts list | Biomedical engineering can reorder correctly years later |
Frequently asked questions
Is the AD16-22 a "medical approved" component?
No component of this kind is "medical approved" on its own. It is an industrial pilot light built to IEC 60947-5-1. What gets approved is the finished medical electrical equipment under IEC 60601-1. The correct way to supply it is as a documented component — datasheet, declaration of conformity, material and RoHS/REACH statements — that supports the manufacturer's own assessment.
Which voltage should medical equipment use for indication?
Wherever possible, 24 V DC from a SELV circuit. It makes leakage-current and creepage assessments far easier, it is safer for service work in clinical areas, and it matches the control hardware typically used. Reserve 230 V lamps for infrastructure panels where mains indication is genuinely required, and never mix two voltage variants in one cabinet.
Can these lamps be used inside an MRI room?
Not in their standard construction. A typical Φ22 device uses steel nuts, screws and terminals, which is unacceptable inside the magnet room — the projectile risk and the image artefact risk are both real, and the site's MRI safety rules govern this absolutely. Where indication near MRI is needed, use a verified non-magnetic design and only outside the area the site defines as controlled.
How do hospital disinfectants affect the lamps?
They are the dominant life-limiting factor for the front end. Alcohol, chlorine-based agents and quaternary ammonium compounds can craze or cloud lenses and harden gaskets over time. Specify a sealed front, confirm lens and gasket compatibility with the agents your hospital actually uses, and include the wipe test in sample approval.
What is a medical IT system and why does indication matter there?
In operating theatres, ICUs and similar rooms the final distribution circuit is often an isolated (IT) system: after a first insulation fault the supply deliberately keeps running so life-support equipment is not cut off. That makes the fault indication the thing that triggers action. Indicate it locally, on SELV, and independently of any network.
Are industrial lamps acceptable on medical gas panels?
They are used on area alarm panels, but the environment must be assessed, because oxygen-enriched atmospheres change material and ignition behaviour. The panel as a whole has to be evaluated for its gas service; use the design the equipment manufacturer has qualified, and keep the indication on a low-energy circuit.
Can one lamp indicate beam-on or radiation state?
No. A lamp that fails dark reads as "no radiation", which is the dangerous direction. Duplicate the lamp or add a feedback contact read by the control system, and prove the arrangement during type testing.
Specifying indication for medical equipment?
MONTOLI supplies low-voltage control and signalling components to medical equipment manufacturers, panel builders and hospital engineering teams — Φ22 indicator lights, push buttons, and the matching breaker and contactor ranges for the same cabinet. Tell us the device type, the disinfectants in use and the voltage standard, and we will match the specification to your documentation instead of guessing.
- Cross-match an existing panel device against all six specification fields
- Datasheets, material declarations and sealed reference samples
- Documented, labelled spare-part kits per device or per department
Note: this article describes general engineering practice. It is not a conformity assessment. Medical electrical equipment must be evaluated as a complete system by the manufacturer and approved by the responsible regulatory and clinical-engineering authority before use.
