Written and maintained by CASRAI Editorial Board
Published · Last updated
This page describes products and general use; it is not medical advice.
On this page
A chair alarm is a weight-sensitive sensor pad placed on a chair seat that sounds an alarm when the person sitting on it lifts or moves off the pad. This page explains how the pad and alarm unit work, how related products (bed pads and under-mattress bed monitors) differ, how the FDA classifies this product family, and what the one large trial of sensor-pad alarms found about falls.
Who uses it: nursing staff, fall-prevention and patient-safety teams, and buyers of patient-room equipment in hospitals and long-term care.
What a chair alarm is
A chair alarm is a pressure-sensing pad connected to an alarm unit. When contact with the pad is broken, the alarm sounds. In the published trial described below, the system used one or two weight-sensitive sensor pads applied to the bed, chair, or commode, and the alarm sounded in the patient’s room and as a call at the central nurses’ station (Shorr et al., 2012). The same hardware family is sold under several names: chair alarm, pressure sensor mat, fall alarm and bed exit alarm. The name usually reflects where the pad is placed, not a different technology.
How it works
The pad senses the weight of the occupant. The behaviour on release depends on the mode the unit is set to:
- Chair mode: in the Shorr trial, an immediate alarm sounded as soon as the patient started to lift his or her body off the sensing pads.
- Bed mode: the sensing interval could be increased from 4 to 8 seconds on the bed pressure pad to reduce false alarms, at the cost of a longer response time to a patient who is leaving the bed.
The trial authors also report that false alarms are a common problem of bed alarm systems in practice and may contribute to alarm fatigue. For how hospitals manage alarm burden in general, see clinical alarm management programs.
Types and variants
| Type | Typical use | Key difference | Source |
|---|---|---|---|
| Chair sensor pad | Placed on a chair seat to signal when the occupant rises | Listed in AccessGUDID under the GMDN term “Bed/chair occupant movement pressure/vibration sensor” (electrically powered sensing pad placed under a bed or chair occupant to detect movement, including exit) | AccessGUDID record for a Dynarex chair sensor pad |
| Bed pressure pad | Placed on the bed under the patient | Same sensing approach; the Shorr trial positioned it between the buttocks and shoulder blades and allowed a longer sensing interval | Shorr et al., 2012; AccessGUDID |
| Under-mattress bed-patient monitor | Indicates when a patient attempts to leave the bed | The only form named in the federal regulation: a battery-powered device placed under a mattress | 21 CFR 880.2400 |
Bed-side detail is covered separately in what is a bed alarm; this page stays with chair and sensor-pad products.
Sizes and specifications that matter
| Item | Size in the record | Single-use flag |
|---|---|---|
| Dynarex Protech chair sensor pad | 10 in x 15 in (from the product name in its AccessGUDID record) | “For Single-Use: No” |
Other labelers list their own pad dimensions; check the manufacturer’s instructions for use for the unit in front of you.
How the FDA classifies it
The FDA’s classification database lists product code KMI as “Monitor, Bed Patient”, device class 1, regulation number 880.2400. Chair sensor pads appear in AccessGUDID under that product code. The regulation text itself, 21 CFR 880.2400, defines a bed-patient monitor as “a battery-powered device placed under a mattress and used to indicate by an alarm or other signal when a patient attempts to leave the bed.” It is Class I (general controls) and exempt from premarket notification, subject to the limitations in 21 CFR 880.9. The regulation text names under-mattress bed monitors; it does not mention chair pads by name, so the chair-pad link runs through the product code, not the regulation wording.
What the evidence says about falls
Shorr et al. ran a cluster randomized trial in an urban hospital of an intervention to increase bed alarm use. Alarm use rose, but the intervention had no statistically or clinically significant effect on fall-related events or physical restraint use. See hospital fall-prevention programs and fall-risk assessment tools compared.
Safe use and handling basics
- Placement, mode and sensing-interval settings are set out in the manufacturer’s instructions for use; in the trial these settings changed how quickly the alarm sounded and how many false alarms occurred.
- A longer sensing interval reduces false alarms but delays the alert (Shorr et al., 2012).
- Pads in the trial were lightweight and flexible, which allowed use on a chair, commode or bed.
Common mistakes
- Assuming an alarm prevents falls: the trial found more alarm use did not change fall-related events.
- Treating “chair alarm”, “fall alarm” and “bed exit alarm” as different regulated devices: the FDA product code KMI covers the bed and chair sensor family.
- Ignoring false alarms: they are a documented contributor to alarm fatigue.
Frequently asked questions
What is a chair alarm?
A weight-sensitive sensor pad on a chair seat, connected to an alarm unit that sounds when the occupant lifts off the pad (Shorr et al., 2012).
Is a pressure sensor mat the same as a chair alarm?
Largely yes. Chair alarm, pressure sensor mat, fall alarm and bed exit alarm are names for the same pad-and-alarm family, usually distinguished by where the pad is placed.
How does the FDA classify chair sensor pads?
They appear in AccessGUDID under product code KMI, “Monitor, Bed Patient”, a Class I category under 21 CFR 880.2400.
Did sensor-pad alarms reduce falls in the trial?
Alarm use rose, but the intervention had no statistically or clinically significant effect on fall-related events or physical restraint use.
Sources
- Shorr RI et al. Effects of an Intervention to Increase Bed Alarm Use to Prevent Falls in Hospitalized Patients: A Cluster Randomized Trial. Ann Intern Med 2012;157(10):692-699. https://pmc.ncbi.nlm.nih.gov/articles/PMC3549269, checked 2026-11-01.
- 21 CFR 880.2400, Bed-patient monitor. https://www.law.cornell.edu/cfr/text/21/880.2400, checked 2026-11-01.
- FDA product classification, product code KMI, via https://api.fda.gov/device/classification.json?search=product_code:KMI, checked 2026-11-01.
- AccessGUDID record, Dynarex Protech 1-Year Chair Sensor Pads 10 in x 15 in: https://accessgudid.nlm.nih.gov/devices/00840117323117, checked 2026-11-01.
