Daily Safety Inspections
Why they are Important & How they Protect Pedestrians
By Michael Panish
Automatic Door Expert Witness
Download PDF of this article here
Why are daily safety inspections of automatic doors necessary?
When an automatic door system is turned off (store closing) and then reactivated
(store opening), there is no guarantee that every component is properly
operating or that the door control is correctly interpreting sensor information.
One of the easiest ways to understand what can go wrong with automatic
door systems is to equate the various components to familiar human body parts.
- Door sensors are the eyes of the door.
- The cabling that connects the sensors to the door control is like our optic nerve.
- The door controller is like our brain.
- The motor is like our muscles.
Like human eyes, several physical components need to be properly connected
and functioning. In the case of a person, it is possible to have a perfectly
functioning eye, but still be unable to see. There is an optic nerve (signal
pathway) which takes the sensory input from the eye and attempts to transmit
it to the visual cortex receptor points in the human brain. If the optic
nerve is damaged or impaired in some way, it is possible that no information
gathered by the eye will be sent to the brain, so a properly functioning
eye can still leave a person blind if the transmission line is defective.
Additionally, if brain receptors are unable to process the transmitted
information, or there are defects in the cognitive abilities of the persons
brain, there is a chance that the person will not be able to interpret
the information being delivered by the optic nerve which results in a
person with a perfect eye being unable to see.
Automatic door sensors (eyes) can have several defective issues that stop
the door control (brain) from receiving or properly interpreting their
sensory output. As with human eyes, the sensors can function as they should,
but the cable (optic nerve) or signal pathway has some defect that hinders
the output signals prior to reaching the door control (brain). The door
controller or “brain” of the system has to recognize, interpret,
and process the activation or presence detection signals sent by the sensors
and send proper information to the motor to open or hold open the door
when the zones of coverage are occupied or obstructed.
There are two basic types of sensors used in common automatic door systems.
One type is activated by motion and is sometimes referred to as an approach
sensor. These types of sensors can be individual units or part of a combined
sensor (motion/presence) product. They rely upon various technologies
using radar-like pinging. Sometimes they are infrared, other times they
are microwave. The motion detection sets up a chain of mechanical responses
that allow a pedestrian to walk through an open doorway before reaching
the threshold. There are minimum activation distance requirements that
must be met to be standard compliant.
The second and most important sensor on all automatic door systems is the
presence detection or proximity sensor. According to industry standards,
once an automatic door is activated, there must be full and complete overlapping
zones of protection between the activation point, through the transition
across the door threshold, and out the other side of the door so that
a pedestrian is observed and protected by these sensored safety zones
of coverage. If a doorway is open, and a pedestrian moves through the
threshold, the presence detection sensor must hold the door in the open
position, even if the pedestrian stands motionless on the threshold for
thirty seconds. It is almost impossible for most people to remain motionless,
and as a result of that, a properly adjusted and aligned presence detection
sensor will hold the door open endlessly.
There is also a timing device built into most door controllers that allow
the door motors to operate once there is a “loss of signal”
from the sensors. In other words, after a door controller “Polls”
or verifies that all the installed sensors have reported an “ALL-Clear”,
the door controller sends a signal to the motor to allow the doors to
move to the closed position.
On all modern sensors there are multiple emitters and receivers that are
used to interpret a pedestrian or other stimulation within the zone of
coverage. Frequently, some of the sensor components become misaligned,
intermittently malfunction, or partially burn out which leads to lack
of information being sent to the door control brain.
On certain presence detection sensors, they may have multiple emitters
that attempt to provide comprehensive coverage over a threshold. If you
position your hand with all five fingers spread apart pointing down and
outward toward the floor it is possible to envision how the multiple beams
of a presence detection sensor can be positioned.
If you bend, lift, or move your fingers into other positions where they
are not pointing directly downward or left or right, you can also observe
how a misaligned sensor emitter can be maladjusted to not fully cover
the entire area as originally planned or required by standards.
In other cases, the “brain” of the door cannot recognize all
of the sensory input and fails to “realize” that there is
a pedestrian obstruction. This is one of the common causes where pedestrians
are struck by closing doors while they are crossing the threshold.
There are recognized defects in some control modules (brains) that require
close scrutiny by the owners of these door systems. It has been observed
that anytime the power is interrupted to the door system, all of the safety
systems need to be evaluated for proper operation and function. One control
module in high use in the industry has been repeatedly found to lose sensory
input information and without verification it appears that the door is
mechanically correct but does not have the “awareness” of
all door sensors. This leads to door impacts with pedestrians if not properly
tested and verified each time the door system is activated each day. Manufacturers
provide information in their owner’s manuals that instruct, inform,
and attempt to teach the end users about the necessity of making “daily
safety inspections” of their doors, but even with applied warning
labels placed near the activation switches, many door owners fail to heed
those words and warnings.
There are many reasons that pedestrians are struck by automatic doors,
however in the majority of personal injury legal claims, proactive daily
safety inspections would have discovered the malfunctioning sensors or
other contributing factors and triggered owners to contact a competent
professional service provider to make necessary repairs prior to creating
injuries to pedestrians.
This article is intended to make all interested parties aware of the continuous
and ongoing need to perform daily safety inspections and improve the safety
of all pedestrian automatic door users. This is not a comprehensive analysis
or complete discussion of the multitude of automatic door operational
concerns, rather an attempt to improve the awareness of the general public
that automatic doors need to be appropriately maintained and routinely
inspected by the people that provide them for their patrons. All pedestrians
should use caution whenever they use any automatic doors.
The automatic door industry, manufacturers, and competent service providers
all agree that properly functioning automatic doors are safe and have
become commonplace in society. No properly functioning doorway should
come into contact with a pedestrian user if the door sensor systems and
all door components are fully functional and properly maintained.
For more information and details that are specific to your personal injury
case, contact Mike Panish, the nation’s leading automatic door expert.
He is retained equally by Plaintiff and Defense and has provided his expert
services to door and door hardware manufacturers, service providers and
installers in defense of claim. He has provided expert services since
the year 2000. For immediate assistance with your claim, whether plaintiff
or defense, contact Sharon at 888 902-4272.