When guests notice an odor in a hotel room, they write about it in their reviews. HotelBank Editorial Team ran NLP analysis on guest reviews from the past 24 months and extracted the 100 properties with the most review mentions of room odor in a negative context, and the 100 with the most in a positive context. The negative 100 drew 12,395 mentions (out of 294,646 reviews analyzed); the positive 100 drew 1,091 (out of 168,277). Negative mentions outnumber positive ones 11.4 to 1: among all room specifications, odor is one that guests readily complain about and rarely praise. This article breaks that imbalance down by hotel type, opening era and room-count band, then sets out per-room renovation cost ranges for ventilation, drainage, interior finishes and deodorizing equipment, and the rate upside that better ratings could unlock, from the perspective of asset managers and facility managers who acquire and renovate existing hotels.

The Asymmetry of Odor Reviews: Voiced as Complaints, Rarely as Praise

Start with the big picture. The top 100 properties for negative mentions of room odor drew 12,395 mentions, with a median per-property mention rate of 5.20% and a maximum of 16.88%. The top 100 for positive mentions drew only 1,091, with a median mention rate of 0.67%. For the same item, room odor, guests overwhelmingly put pen to paper when something is unpleasant; a pleasant smell is mentioned in fewer than 1 review in 100.

Comparing adjacent items shows how large this skew is. The top 100 properties for negative mentions of room “tobacco” drew 2,395 mentions (median mention rate 1.15%), and the top 100 for negative mentions of “ventilation” drew 2,398 (1.28%), each less than one fifth of the negative odor total. As for reviews praising ventilation, only 36 properties nationwide reach 5 or more mentions. Odor is the “end symptom” guests perceive as the result of specific causes such as tobacco, poor ventilation or mold, and it is written up as a single complaint whatever the cause. That is why the counts pile up.

Notably, 29 of the negative 100 also appear in the top 100 for negative tobacco mentions, and 36 in the top 100 for negative ventilation mentions. Roughly a third of the hotels with many odor reviews are also criticized for tobacco or ventilation, confirming that odor is not an isolated phenomenon but is written up as the combined result of facilities and operations.

What Guests Actually Smell: Tobacco, Mold and Drains Make Up 90%

So what odors are guests writing about? From the reviews of the negative 100, we extracted 1,000 snippets; the editorial team categorized the 255 that referred to the odor itself. Of the 134 where a cause could be identified, tobacco accounted for 49 (37%), mold and damp for 43 (32%), and drains and plumbing for 32 (24%): these three types make up 90%. The remainder were body or food odors (5), smells from the air-conditioning outlet (4), and air freshener or hair-product odors (1). In 121 reviews only the location was given, such as “the bathroom smells” or “the towels smell”, and the cause could not be identified.

Note: Quotations are partial excerpts from reviews, translated from Japanese (HotelBank Editorial Team research, past 24 months; the 134 of N=255 reviews where a cause could be identified were categorized). Property names are withheld. The categorization is a simple editorial classification; where a single review cites multiple causes, it was counted under the first matching type.

The 37% share for tobacco is not unrelated to the fact that hotel guest rooms are exempt from the indoor smoking ban under the revised Health Promotion Act that took full effect in 2020. Where smoking and non-smoking rooms share a floor, odor migrates through shared HVAC and exhaust paths between rooms and through unauthorized smoking in non-smoking rooms. In a July 2025 survey of 719 smokers by Ergo Japan, 45.8% of cigarette users said they “always choose a smoking room”, yet 32.2% (39.0% among heated-tobacco users) cited “bothered by the smell of cigarettes” as a reason for choosing a non-smoking room, and 27.8% had smoked inside a non-smoking room when no smoking booth was available. Smokers themselves choose non-smoking rooms to avoid the smell, and some smoking then takes place in those same rooms. This cycle is what feeds “non-smoking room but smells of cigarettes” reviews. How smoking-permitted room plans have shrunk to 2.6% of all plans at 888 properties, unevenly distributed by hotel type and opening era, is covered in Smoking Rooms: 2.6% of Japan’s Hotel Plans.

Profile of the Negative 100: Business and Resort Hotels Aged 26+ Years With 200+ Rooms

By hotel type, the negative 100 comprise 41 business hotels, 27 resort hotels, 22 city hotels, 8 ryokan and 2 others; by mentions, business hotels account for 4,907, resort hotels 3,449 and city hotels 2,842. The positive 100 comprise 43 business hotels, 23 resort hotels, 18 ryokan, 13 city hotels and 3 others, so the type mix itself differs little between the two groups. Odor reviews are not a phenomenon of any particular hotel type; they occur in similar proportions at business hotels and resorts alike.

The differences lie in opening era and scale. The negative 100 have a median opening year of 1996, and 58 opened before 2000. The positive group is a near mirror image, with a median opening year of 2017 and 54 opened in 2010 or later. By mentions, the 21 negative-group properties opened in 1979 or earlier lead with 2,927, or 139 per property. The 7 opened in 2020 or later account for 871, or 124 per property; that is still substantial, and it is worth noting that odor is reported even in new buildings.

By room-count band, 46 of the negative 100 have 200–399 rooms and 31 have 400 or more, so large properties with 200+ rooms account for 77. The median room count is 323, and the 100 properties total 41,795 rooms. In the positive group, 26 have 49 rooms or fewer and the median is 176, so small properties are more common. Statistically, larger properties have more reviews in total and so more easily rank high on absolute counts. Yet comparing median mention rates (mentions divided by total reviews), the gap persists at 5.20% for the negative group versus 0.67% for the positive group, so scale alone cannot explain it.

Reread from a facilities standpoint, “26+ years old with 200+ rooms” describes buildings with ducted ceiling ventilation, central air conditioning and drainage connected to shared vertical stacks. In buildings without individual room ventilation, where room air is determined by the supply and exhaust balance of each floor, smoking in one room or odor from one drainpipe easily spreads to adjacent rooms and the floors above and below. It is a natural interpretation to attribute the concentration of older, larger buildings in the negative group to this building-side structure. How equipment renewals, including HVAC heat sources and elevators, overlap at properties opened between 1991 and 2001 is analyzed in terms of stock size in 214k Hotel Rooms Aged 25–35 Face Equipment Renewal.

By Prefecture: Negatives Led by Chiba, Tokyo, Osaka and Fukuoka; Positives by Tokyo, Shizuoka, Kyoto and Fukuoka

The negative 100 are located in Chiba (16 properties, 2,174 mentions), Tokyo (12, 1,565), Osaka (9, 988), Fukuoka (8, 975), Kyoto (6, 683), Shizuoka (6, 741), Hokkaido (5, 675) and Tochigi (5, 636), in that order. Areas with clusters of large resorts and urban business hotels rank highest, with high review volumes feeding directly into mention counts. The positive group is led by Tokyo (12), Shizuoka (8), Kyoto (8), Fukuoka (8) and Kanagawa (6), with small highland and hot-spring resorts prominent, such as Nagano (5), Mie (3) and Ishikawa (3).

Viewed on the map, the positive 100 form two clusters: new business hotels in city centers, and pet-friendly resorts in places such as Karuizawa, Izu, Lake Hamana, Nasu and Awazu. As the next section explains, the latter is a segment where “no odor” is an evaluation axis that genuinely surprises guests.

What the Positive Group Shares: Hotels Where “No Smell” Is a Compliment

Among the properties with the most positive mentions, 16 of the positive 100 advertise pet-friendly stays in their names, including 7 of the top 15. Reviews such as “a dog-friendly inn, yet there was no smell at all”, “a pet hotel, but there was absolutely no odor” and “clean, with no dog smell in the room” line up: the more guests arrive expecting an odor, the more its absence is written up as clear satisfaction. Conversely, at an ordinary hotel guests take the absence of odor for granted, and it is almost never praised.

The other type is the hotel praised for its scent design itself: “a hotel that smells nice”, “it smelled really good and I felt soothed”. At Hotel Metropolitan Kamakura (ホテルメトロポリタン鎌倉), opened in 2020 with 138 rooms, 24 of 2,357 reviews (1.02%) spoke positively of the smell, describing the in-house fragrance as a memorable part of the stay. At properties that have moved from “eliminating” odor to “designing” it, scent works as a differentiator in reviews.

In facilities terms, what the positive group shares comes down to three things. First, a fully non-smoking building: none of the new business hotels and resorts at the top of the positive group allow smoking in guest rooms. Second, per-room ventilation: since the late 2010s, new builds have standardized on designs with supply and exhaust in each room, so odor from neighboring rooms is less likely to travel. Third, scent design: placing a consistent fragrance from the lobby to the guest rooms means any lingering smell is perceived as “that hotel’s scent”. As Hankyu Hanshin Hotels showed in 2019 when it made all 4,380 rooms at its 15 directly operated hotels non-smoking and installed smoking booths inside and outside the buildings, existing hotels can meet the first condition through an operating decision. The second and third are matters for renovation investment.

Per-Room Capex by Renovation Measure: From ¥10k–¥30k for Drains to ¥100k–¥180k for Energy-Recovery Ventilation

This brings us to the core of this article. We set out the renovation measures that address the three odor types as per-room cost ranges. Where published prices or case studies could be confirmed, sources are given; labor and quantity assumptions are explicitly marked as “this article’s assumption”. The assumed room is a double or twin of about 20 sqm, with 60–80 sqm of wall and ceiling finish area.

Combining the measures, the operations-led “Light” package (A+B+C) costs ¥50k–¥100k per room, the “Standard” package that extends to interior finishes (A–D) costs ¥150k–¥300k, and the “Full” package that adds new in-room ventilation (A–E) costs ¥250k–¥480k. Hotel construction costs in 2024, based on MLIT’s Building Construction Starts statistics, averaged ¥1.95M per tsubo (about 3.3 sqm) across all structure types, a record high (HOTELISM gives ¥1.0M–¥1.5M per tsubo as a guide for building a new business hotel). Compared with the cost of building the floor area for one roughly 20 sqm room from scratch, even the Full package amounts to only a few percent. The higher the cost of new supply, the more attractive investment in improving the room environment of existing buildings becomes.

Sequencing matters, however. HONU points out that replacing wallpaper alone often fails to remove odors. Tobacco and mold odors persist in indoor HVAC units, ducts and carpet underlays, so doing D’s interior work first risks the smell returning right after renovation. A phased approach maximizes cost-effectiveness: cut off the sources with A, B and C, then move on to D, and consider E only in buildings where odor still flows in from adjacent rooms or common areas.

Better Ratings and Room Rates: A 0.16–0.38-Point Review Score Gap Within the Same Price Band

How does odor renovation affect revenue? Causality cannot be measured directly, but lining up negative- and positive-group properties within the same price band shows the rating gap. The estimated settled ADR (median, past 12 months) is ¥13,100 for the negative 100 and ¥18,400 for the positive 100. By type: business hotels ¥12,000 vs ¥14,400, resort hotels ¥14,200 vs ¥20,800, city hotels ¥13,400 vs ¥21,700, and ryokan ¥13,600 vs ¥17,700. Because the positive group opened more recently and has fewer rooms, most of this gap reflects differences in building generation and location and cannot be attributed to odor alone.

So we compare overall review scores within matched price bands. Below ¥10k estimated settled ADR, the median was 3.64 for the negative group (25 properties) vs 4.02 for the positive group (10); at ¥10k–¥15k, 3.96 (28) vs 4.12 (18); at ¥15k–¥25k, 3.89 (23) vs 4.15 (43); and at ¥25k and above, 4.21 (8) vs 4.41 (19). The positive group scores 0.16–0.38 points higher in every band, with the largest gap below ¥10k (0.38 points). One interpretation: in the low price band guests factor in older facilities to some extent, so odor, an “unexpected discomfort”, moves the score more easily.

As a guide to translating this gap into room rates, HotelBank’s analysis of bedding (Bedding Reviews: Sleep Comfort Moves Ratings 0.2 Pts) likewise observed a gap of around 0.2 points across all price bands when looking at how much rates can rise when ratings improve within the same price band. Conservatively, this article sets the ADR uplift from odor renovation at three levels, 2%, 4% and 6%, and estimates payback years assuming the negative group’s median ADR of ¥13,100 and 75% occupancy (full-year, this article’s assumption). Both the occupancy and the uplift rates are this article’s assumptions.

For a 300-room property (close to the negative group’s median of 323 rooms), the Light package totals ¥24M and even the Full package ¥108M. In a cautious case where the ADR uplift is only 2%, the operations-led Light package pays back in just over a year and the Standard package, including interiors, in about three years. The Full package with energy-recovery ventilation takes five years, but brings additional benefits in energy savings and maintaining ventilation volumes in winter. Winter, when heating season leads operators to cut ventilation, is also when odor reviews tend to appear. If renovation is planned for the January–March low season, a realistic phased approach is to first cut off the sources with A–C, then proceed to D and E investment decisions while checking in 3-month increments whether the review mention rate falls.

Sensitivity Analysis: Occupancy and Uplift, Three Scenarios, and Payback by Hotel Type

Table 3 fixes occupancy at 75% (full-year, this article’s assumption), so we also check the range when the occupancy assumption moves. For the Standard package (A–D, ¥220,000 per room), lining up payback years across combinations of 65–85% occupancy (full-year, this article’s assumption) and 2–6% ADR uplift gives 3.5 years in the toughest case, “65% occupancy (full-year), 2% uplift”, and 0.9 years in the most favorable case, “85% occupancy (full-year), 6% uplift” (Table 4). Payback responds far more to the uplift than to occupancy: a 10-point move in occupancy changes payback by only 0.1–0.4 years, whereas raising the uplift from 2% to 4% roughly halves it. As a measure of renovation success, maintaining and raising the rate should be tracked ahead of occupancy.

In three scenarios that move cost and effect together, the pessimistic case with Capex skewed high and effect skewed low (¥300,000 per room, 2% uplift, 65% full-year occupancy) pays back in 4.8 years, the middle case (¥220,000, 4%, 75%) in 1.5 years, and the optimistic case (¥150,000, 6%, 85%) in 0.6 years. For 300 rooms, the total ranges from ¥45M to ¥90M and the annual revenue gain from ¥18.65M to ¥73.16M (Table 5, upper rows). Substituting the negative group’s median ADR by hotel type, at 4% uplift and 75% occupancy (full-year, this article’s assumption), Standard payback differs little at 1.4–1.7 years; even business hotels, with the lowest ADR (¥12,000), pay back in 1.7 years (Table 5, lower rows). Odor renovation is an investment that can plausibly pay back within three years regardless of hotel type, even including interiors; what drives the payback period is not the hotel type but whether the property can sell out after renovation without cutting rates.

Conclusion: Odor Is the “End Symptom”; Renovate From the Source Outward

For guests, room odor is a single complaint regardless of cause; for operators, it is the combined result of ventilation, drainage, interior finishes and smoking policy. As the negative group’s profile shows, in buildings where age, scale and floor-level ventilation coincide, odor in a single room can easily affect the rating of the entire property. At the same time, the positive group shows that some hotels have turned odor into a differentiator through a fully non-smoking policy, per-room ventilation and scent design. Source-level odor measures that start at ¥50k per room are among the investment opportunities in a post-acquisition value-add plan that show up in reviews the fastest.